Routers use many different ports for different things. For instance: port 80 is the standard port for surfing the internet. Port 22 is for SSH servers, 110 is usually for pop3 email protocols. So when they say port number they're probably wanting you to port forward a certain port (this means that your computer now allows connections like a server through the port that you specify).
I'll warn you though, port forwarding is dangerous if you don't have a good personal firewall, as it's like a by-pass to your router security.
To do a port forward you go into your router settings, depending on the router it could be anywhere really. Either advanced, server settings, or perhaps virtual server tabs.
After you forward a port you can tell Bittorrent to use that port and security won't be slowing you down as much. So theoretically it is faster, but it's up to you if you want to take the slight security risks.
Edit: The number that gorgi and raj are describing is your MAC-Address. This is specific to your router, usually used so that the government can track you down.
To Capt_: just because someone's using Bittorrent doesn't mean that they're using it illegally, p2p has other purposes as well.