OK, for 'clarity';
The 'green box' auto, is the 'default' full auto, point and shoot exposure program. The icon modes anti-clockwse of that are ALSO all FULLY automatic exposure programs; but tailored to better suit different subjects as denoted by the icon. frist circle with a lighting strike in it, disables the flash; so promts the program to select higher ISO's and wider apertures and slower shutter speeds, rather than add light. Woman in the hat, is 'portrait'; it's program will favor less aperture for a shallower DoF around that subject, and probably a brighter exposure assessement based oskn tones and likely face shaddow. Mountains in the box; is 'landscape'. That program will likely favour tighter apertures, in order to maximise front-toback DoF in the scene and get near and far scenary all n sharp focus, whilst it will likely let shutter speeds drop, as mountains dont ted to move very far or fast so unlikely to crate motion blur. Next is the kid in a hat, or full length portrait; Here the program will likely favour a little less aperture to keep more of the subject in the DoF zone; running man next is 'sport', so program assumes stuff will likely be moving a bit fast, so favour faster shutter speeds in order to avoid subject blur; the tulip is 'macro', for very close focus subjects, agan it will lkely tweek the exposure to account for likely lghting anomoles over such small area of scene, and probably favour smaller apertures to get a decent DoF at such close rage where they can otherwse be razor blade thin. Next box s 'night-time' which again props a shft in the program to not try ad compensate exposure so much, trying to make a predominantly 'dark' scene brighter than it is, assuming 18% grey 'average'.... THAT is 'sort' f how they work. They are ALL fully automatic exposure programs; you do NOT make individual exposure settings. Camera chooses settings from exposure metering, entirely to 'program'; all the icons do is give the camera a better clue which settings may be more suitable for a situation, as YOU look at it.
A is aperture priory; 'semi-auto'. You set the apertre you think best, camera sets the shutter speed to balence the meter needle against it. S is shutter priority, same deal other way about; you set the shutter speed you want, camera selects the aperture to balence the meter needle. 'M' is full manual; you set both shutter and aperture; all the camera does s give you a bar display the view-finder to tell you whether those settigs youchose are likely to resutt n over or under exposure, compared to the cameras meter readig and assumption of 18% average reflected light. 'P' is a mongrel.It's an fully auto-mode, but one where in the menu's you set thresholds to tell it when to stop dropping shutter speed or upping the ISO to balence the needle, before you start
So there s only ONE 'manual' mode; and that s the 'M' settngs. A&S are semi-atuo, P s a user programmemed fully auto; all the others are fully-auto, to pre-deturmined 'program'. Icon settngs being situation dependent, allowing yo to gve the camera better clue which program would be better; green-box is the default, best guess fully auto mode... got that?.
There is only ONe 'manual' mode, and that's 'M'. Everything else is auto.
You have an 18-55 'kit' zoom... Here and now that is likely the ONLY lens you need experiment with. It's actually a great lens for the money.. ie less than free when they give it away in 'kits' often cheaper than the camera body only! In the last five years, since grudgingly went Digtal SLR, and tried building p a kit with the same sort of range of versatility as my film cameras, THAT is actually my most used, first go to lens; there's more quids worth of 'other' lenses n the bag than camera! And seriously, look in the bag, ad am embarrassed have spent SO much money o other lenses to hardly get used, and yet STILL have that lowly 18-55 on the front most of the time... it is a great lens, and for what you suggest you are doing 'brilliant'.
The 70-300; you don't say which one it is, the much vaunted Sigma, perhaps? As a GP telephoto, it is a very well regarded lens; if the Siggy, it's actually a 'budget' full frame lens, so a lot of the applause it gets for use on APS-C sensor cameras comes from the crop factor stretching its effective focal length, and only making a picture fro its 'sweet-spot' in the center of the mage circle. But.. such techno-nerdery probably isn't all that pertinent to you here and now.
MY STORY; To get some useful added reach, I bought the Nikon 55-300 'kit' tele wth my DSLR.. it's not a fantastic lens, but it is useful, and on a crop sensor body, with the 'tele-magnifying' effect of the crop factor, that 'gap' between where the 18-55 runs out and the 70-300 starts is that bit more critical, AND I find I more often am using the longer lens, down in that 'gap' region and the shorter focal lengths of it's zoom range.. in rationalizing the glass-I-got, acquiring a fish-eye was first indulgence, after having one for my film cameras; little used, but if hadn't got one, early on, I figured I would forever be putting off ad putting off! Next came a UWA 8-16, as I had always favored the wider lenses on my film cameras, and that gt e down and beyond the range I had for film. That 'sorted'.. I look at the 18-55 ad as said feel embarrassed its the cheapest lens have yet the most oft used... and ponder what would make a good 'upgrade'... so far it has dodged three Christmas present lists... and still remains!!!
I days of yore, on manual focus fl cameras, 50mm was the 'standard' normal angle lens.... most compacts had a fixed 35mm lens, which was probably the more useful all round general purpose lens on a 'full-frame'. The 50mm was what came with SLR's, and a lot of academic exercises were written around, and was often the ONLY lens many folk ever had. When zoom lenses started to become popular, the pretty meagre range of a 2x zoom 35-70, was the favoured 'stadard' lese offering justthat bit more wide and that bit more tele ether side of standard.
Translating to Digital, with smaller APS-C sized sensors; the 'normal' angle of veiw a 50mm provided on film s actually about 35mm give or take, ad the 18-55 'kit' lens has an effective zoom rage, of 27-82mm on a film camera; it is a VERY useful zoom range, with even that bit extra ether side, of a less common 28-80 'standard-zoom' for a film camera. With that sort of range of 'framing', it is no wonder it s my most used lens, and it really does cover that 'most used' range of framing angles
Little aside about the 50mm prime; as mentioned these were often the 'kit' ens that came with old film SLR's. They were often very good lenses, and commonly had particularly 'fast' widest apertures.But, they were often rapidly side-lined n favour of alternate lenses, as folk built their kit, ad aquird a greater range of primes or a zoom or two. Personally, in my ow 'film' career, I had a fatastic 50mm Zoiko f1.4 for my Olympus SLR's as well as a couple of the lesser f1.8 examples.. ALL of which were effectively given away 'in the day' as they just weren't used. I still have the rather lovely Ziess 50 for my M42 fit film camera, but even that was and remains little used, and for walk-about, the Pentacon 28mm 'wide angle' far more often found on its mount. On the Olympus's a 35-70 or 28-80 were the most used lens, covering the range of three primes. HOWEVER; as Digital Cameras came in, often able to mount older film era lenses,those 'old' 50mm primes became re-popularised as Digital-Era folk discovered 'primes' ad read 'old' film era tutorials that were written around film era 'standard' 50mm lenses.. BUT the 'crop factor' that shifted a 50mm lens from a 'normal' angle of view to that of a 'tele' in the 75mm range, was either over-looked, ignored or accepted.. but that 'vogue' to start using 'old' prime lenses from film cameras has re-popularized the prime, and lead Nikon to actually offer thier 'budget' AF-35mm for digital, that does have that 'normal' angle of view on an APS-C camera as a 50 had on film, with a rather 'fast' f1.8 maximum aperture.
Oh-Kay.. when daughter started chucking water-filled balloons about in close proximity to my rather expensive electric picture maker, for her GCSE photo course; I bought her a second hand D3100 and a 35mm prime, if only to save my camera getting drowned! the 35mm prime, on an APS-C digital, is a close equivalent to an old film camera with a 50, and was great for her school photo' stuff, followng the accademic excersises set, with a lot of legacy of the film era and a film camera and 50 combo. I later got her the 50mm prime, when she started doing more studio portrature; as it des sort of equate to the perspectve flatterg framing of short tele's for flm; BUT for a lot of stuff, on digtal, 50mm IS a bit neither nor. Its not a standard angle lens, nor is it particularly tele-photo, and it is a bit 'suck' up at the tele end of the kit 18-55 and only offers the fast aperture for shallow focus effects in compensation for it. For where you are at, great a lens as it may be, I thik that ne is likely a distraction to doing very much. If you want to start playng primes; the 35mm would be the more useful, I suspect, but either way; for where you are at, they are something likely to hider rather than help you at the moment.
The 70-300 tele; probably a very good lens; and if you were birding or trying to get close up 'action' of out-door sports, would be very good; though, for a lot of things say school sorts-day, that gap between 55 & 70, could likely be the bit you miss, and the bit from, maybe 180 to 300, not dong a lot for you, bar encouraging you to use too much zoom, cut out context, and generally make life hard for yourself, making focus that much more critical....
On film; my 'long' tele was (and still IS actually!) a rather nice Vivitar Series 1, 70-210. That has the equiv angle of view of 43mm-140mm on a crop-sensor digital camera. I did/do have longer, but believe me, for school sports day, snapping my sons socker matches; catchng shots of my daughter's ice skating, etc etc etce, THAT was my go-to glass, and had more than enough 'reach' to get in on the action and fill the frame with subject. That DOES actually beg suggestion that a modern 18-140 'super-zoom' IS probably a damn useful all round general purpose 'do-it-all' lens, and IF were to upgrade the 18-55 kit, one of the would like as not be a good bet, and not just mae the 18-55 redndant, but the 550-300 too, for all that 'extra' zoom gets used!
But, lakng that first half of the zoom range at the wide-end, that does sort of suggest that you probably DONT need to reach for the 70-300 very often, if at all, AND if you are on the learnig curve, I WOULD strngly reccomend that you leave it o the shelf or the bag; and conentrate on making the most of the 18-55 'standard' lens, for ow. and concetratng on getting the picture; avoiding moton blur, controllng DoF, and basics of thngs like camera holding, panning, tracking and all teh other stiff that is outside the camera and doesn't beg twiddling buttons or knobs!
Again; learning i the film era, we didn't have them! We had a shutter release and a film advance, and a focus ring to worry about! THAT was enough!.Making better pictures was to be found looking THROUGH the camera not at t!
In conclusion then:Of what you have; the 18-55 kt lens is probably the most useful, usable and versatile lens you have, and likely far more than you really 'need' for most of what you are dong, and more. And I would recommend you put t on the camera, and leave it there as a first course choice, and NOT look for reasons to try the others you have, but, WHEN you start running up against the buffers of what you can do with the 18-55, by zooming with your feet, getting close by getting close or getting it all in by backing off; looking for better angles moving around your scene, looking for alternate angles, crouching down, or getting up high, etc etc etc rather than trying to make the shot with the zoom ring from wherever you happen to be stood; Then you might ponder swapping lenses.
For NOW, in a welter of confoundmet over exposure settings and alternate lenses and what lenses to use for dfferent subjects? KISS me! Keep-It-Simple-Stupid! Eliminate the variables. Stick to the ONE lens, the 18-55. It is still far more than we ever had starting out with film cameras! And it covers that most used, most useful range from wide angle to mild tele-photo either side of 'normal', And you could likely get better results eliminating even that complication; sticking to say 30 or 30mm or 35mm wide angle, and trying to use it like a prime!! NOT touching the zoom-ring, and worrying about framing with your feet; gettig up close, moving back, gettng high, getting low, ad concetrating on compesition... as said, Sod the settings, worry about getting good photo's! Camera knows sod all about what its pointing at, only YOU know that; concentrate on that bit only you can do, and let the camera do the stuff it probably does better, right now.
Back to the exposure settng dial? That green box.. hated by many, is bludy useful! IF you cant decide which alternate icon, gives the camera a little better idea what exposure settings may or may not be more or less apt for the subject YOU are looking at; USE the ruddy green box! That is what it is there for!
Stop looking at the camera and all the gadgets in the bag and making things more complicated than they need. Keep it simple; expect failure, and dont blame the camera for your mistakes. Don't look to the hardware to solve your problems; look to learn, but most important, practice, practice practice! And remember, great photo's happen OUTSIDE the camera, not in it! Look THOUGH, not AT it!