In a script you must include a #! on the first line followed by the path to the program that will execute the script (e.g.: sh, perl). As far as I know though, the # character denotes the start of a comment and that line is supposed to be ignored by the program executing the script. It would seem though, that this first line is at some point read by something in order for the script to be executed by the proper program. Could somebody please shed more light on the workings of the #! ?

Edit: I'm really curious about this, so the more in-depth the answer the better.