It is part of the way linux is set up.
It's a bit the same as how the user nobody
exists. Delete that at your peril (I did as a complete newbie, and a reinstall was required
For more information please search http://google.com/linux
But your "what's going on in this OS" curiosity is to be commended. Linux is "open", so you can find out what everything is there for, and exactly what it does
Search on, you do not need us.