It's an area the OS uses in case you fill up your RAM. Think of it as a
scratch pad Linux uses when to many things are happening.

swap space is a partition on your hard drive to be used as virtual
memory when your psysical ram gets used up. What happens is your
processor writes and read to the swap partition to keep things going. It
is much slower than normal ram and the puter slows down. I have 1
gigabyte of ram in this machine and 512 meg of swap. the swap never
seems to get used.

So if I have 768 mb of ram then my swap probably
doesnt get used either.

I have a 1 GB swap partition and 1 GB of ram. I hardly ever use swap space :)