You can organise your photos by subject, location, or whatever, and Lightroom will mirror this organisation, i.e. it will show you the folder structure that's actually on your hard disk. You can also organise them in sets; you could have a set for all of your portraits, another for landscapes, and so on. You can also assign tags and search for all photos containing a particular tag. You can also search for photos by camera used, lens used, aperture used, whether it's a JPEG or RAW file, and so on. You can search for text inside any EXIF or IPTC field. And you can assign stars to rate photos and/or colour codes for whatever purpose you can think of. I'm sure I've missed out one or more feature; I'm in Linux at the moment so I can't run Lightroom to check.
Workflow is the sequence of jobs you do from the time you get the photos off your camera all the way through to printing and/or uploading to the web. For example, using Lightroom it can include:
- copying RAW files or JPEGS from to your PC from your camera via USB or from the memory card
- synchronising Lightroom so that it finds the photos; or importing them specifically from a particular hard disk location
- looking through the photos, deleting the obviously unviable ones
- star-rating them, assigning tags, deciding which to process now and which to leave until later
- filling in the IPTC and EXIF header information
- doing preliminary tonal and colour corrections, initial noise removal and possibly initial sharpening
- applying gradient filters, removing red-eye, spot removal
- taking photos into Photoshop, Elements, PaintShop, or whatever, to do cloning, healing, filters, portrait touch-up, or anything involving layers
- applying any finishing touches to colour and tone, final sharpening
- uploading to the web if you have a portfolio or a Flickr/500px/Photobucket/whatever account
- printing your photos
If you're a professional, there are a few other steps involved, depending on the type of work you do.