When I go into photos, there is a choice of photos, photo stream, albums and places.
Photos has all my photographs and they seem to stay there unlike photo stream. When I go into albums there is something called camera roll, I think it has all the same pictures (although I'm not sure there are so many I get confused trying to check back and forth). What is the difference between photos and camera roll? Why do I have two things that, at least to me, seem to be the same?

Photos shows all pictures, including those synced through iTunes or imported from a camera. Camera Roll only shows pictures that you have taken, or created and saved on the iPad. Screen shots also show up there. If you've never imported or synced photos to your iPad, they would be the same.