Code golf is the practice of trying to implement some functionality in as small a program as possible (usually counted in terms of characters of source code). It's a type of a recreational programming activity and the basis for a number of online competitions.
Here's a fine example written in C.
main(l){main(8^putchar(l++["xx77Rd$fR\a$wP\aP"]^88)?l:26+fflush(sleep(1))-l);}