From LQWiki

Garbage Collection

Term used to describe freeing up memory. Garbage is the memory that was written to by the program and no longer needed. Garbage Collection is freeing up memory space for other programs to use.

The programming language Java does this automatically, though other languages require you to do this manually. (such as C and C plus plus )

Windows 98 is notoriously bad at doing this- with out a restart every so often, it will crash because of lack of memory. Some universities have competitions to see who can get a Windows 98 computer to run for the longest- the record is about five days. Linux boxes on the other hand are much better at doing this- some people talk of computers running continuously for years!