Good point Plum.
Irc = Internet Relay Chat. You can download the program at: http://www.mirc.com/
It's really simple to use. Just need to connect to the right server. The program will already have a list of servers, just go down the list until you find a efnet server. If you don`t see any, here are some you can add to the list:
I know they don`t say Efnet but trust me they are. You will need a nickname, sometime the one you choose is already taken, in that case use your imagination and select another one.
Once connected, you need to join the chat room. You will see a status window, click on the line and type:
And voilà you will be in. Any question?