The editing process starts with a critical examination of the image. Quite often it can end there as well. This is still 'editing' (you may want to think of it as 'quality control') as you have produced an end result of the photographic process that pleases you. A very high proportion of images will tend to benefit from some post-production tweaks, and these will vary depend on what you plan to do with the shot. A picture you plan to print as a big, framed image to go on a wall will quite likely need more work than a low-res image that will only be seen on the web, as any faults will be magnified - sensor marks for instance. Digital photos mostly benefit from some sharpening as well, and this is generally best done in post where you can see the shot at a decent size and apply the sharpening each picture needs. Or not.