What is a BNC
BNC's is an internet relay chat proxying server. It allows users to connect to chat servers in this case swiftirc by bouncing off the computer which is running the BNC. The BNC will has given you will allow you to be connected to irc and receive private messages even though you have turned of your computer.
If you /whois YOURNICKNAME you will see a different Host to what you usually had. This is mine with the BNC
NICKNAME is will2@Swift-1C2796E0.info * Will BNC
ADVANTAGES
When you disconnect your nick will still be online
You can still receive private messages
DISADVANTAGES
A little more lag when you first start connecting
Your host looks different