SILC is a chatting protocol much like IRC. However, SILC is focused on security, and channels don't start with a #. It stands for Secure Internet Live Conferencing.
There are currently two clients for SILC. One is the official SILC client which is run in a text console, or terminal. The other is Pidgin.
One: Hey, let's chat on this new SILC thing, instead of IRC.
Two: What's the use?
One: I need to tell you government secrets and SILC is more secure!
Two: Umm... ok.