It's a linux psudo random number generator. It uses a seed from a bunch of fairly random stuff and basically just provides you with a reasonably random number when you need it. If you write C/C++ there is a pretty good chance that when using the random number library it is fetching that number from /dev/random. Try using cat to send it to your sound card sometime or to your teminal. Remember if sending it places that the "reset" command on the terminal is useful ;-)