A supercomputer is a computer system that is considered to be the fastest and most powerful at any given time. These systems are used for purposes that require an enormous amount of processing power.
The first instance of a supercomputer, aptly named Colossus, was used by the Allies during the second World War to decrypt German codes. Supercomputers, while still having many of the same components of traditional computer systems, generally have advanced hardware. For instance, NASA's Columbia supercomputer has multiple CPUs rather than the single processor found in household computers. This gives the computer a lot more processing power and enables it to perform a half trillion calculations per second.