Replying to Newb question about camera file names

when you look at the files from a digital camera, they have some kind of name (ie GRPR0933, PICT0543, CIMG2231). these names are all unique to every single shot, regardless of memory cards or resets right? what I'm trying to say is, the first shot using memory card one on my camera will have a different name then the first shot on memory card 2 on the same camera, right? and do firmware updates/formats change this? and when do the numbers go back to zero?

that probably sounded really confusing, im in the process of going through my harddrive which is a mess full of numerous copied files, and am worried about accidentally deleting stuff.

massive +k to anyone who can help.