Port forwarding.. Is there a plain, easy n00b guide?

[jotto]

Have just bought and set up new adsl modem/router to link two pcs to share an internet connection.

Before the router It was a case of I had the net, shared a few files over the network and that was that.

I play alot of games online and have seen lots of posts regarding port forwarding in the router.

What exactly is it? how is it configured and is it necessary?
Boths pcs run norton antivirus and internet security...yeah i know but they seem to run ok and appear to be doing their job...

so, any help out there?

[rraehal]

Here is one that is often posted here:
http://www.ezlan.net/routers1.html

Here is another:
http://www.portforward.com/routers.htm

[jotto]

Thanks for prompt reply, will check out the sites now.