Can someone explain the differences between Post Processing software?

Cool. Thank you for the help. And yes in iPhoto if I just quit the program everything is saved somehow. That is why I thought that because the photo adjustment is still saved somehow, I thought there would be some loss. It must be something specific with iPhoto that saves everything with out having to actually hit the save command.

Anyway, I think I'm slowly getting it. Thanks again and sorry for the incessant questioning.