Multiplayer FAIL...

First off, i know that to some, this question is RETARDED, but im not that smart on this stuff so i dont know what the technical crap means.

Its pretty simple, i want to play online with my friend, so i hit Create Multiplayer and started on a CSS map, when he goes to join, it cant connect to my game, why does this happen?

I can’t join my friend’s LAN game/I can’t see servers I’ve made with Create Server.

This requires you to forward some ports on your router. There’s tutorials on how to do this all over the internet, and also www.portforward.com