*.bin files, coupled with a *.cue, can store a copy of a CD "as is", sector per sector. If you have a *.bin of a CD, you can burn it onto a CD using the appropriate software (ex. Ahead's Nero, or CDRWin). Certain programs allow the editing of *.bins, so you can add or remove certain files from a CD. They are very useful to crack software, as you can create a *.bin on your hard drive, patch it, and then burn it onto a CD again. This is the technique used most frebuently in creating backups of Playstation games