[mayoman]

Can someone link me to how the swap files works and what it does. I had a quick google but cant find much about it.

Analogous to a pagefile in Windows, swap files are used in Linux to swap data out of RAM. Necessary where you have limited RAM, not really needed on systems with lots of RAM except for suspend function where the data held in RAM is dumped into a swapfile. In some systems a whole partition is set aside for swap, though more commonly now just a file. Most Linux systems will by default do some swapping unless told otherwise (there is a value called swapiness that you set to a value between 0 (swap only as a last resort) to 100 (swap as aggressively as possible to preserve RAM).
Ubuntu Wiki on the subject here.