a collection is a random gathering of images chosen by the staff using some kind of incantation to be chosen. its unknown why the things are chosen the way they are, however you have no control over that. galleries are directories for your images to go into. it keeps your store organized. and groups are the places everyone can send their images into and those are set up by volunteers (many confuse this area as a place to put their own work).
---Mike Savad
MikeSavad.com