Netsplit: When the users are overloaded in IRC, one or more servers sometimes split from the IRC server. However, these servers keep communicating with each other. This is known as netsplit.
Lag: Sometimes a message takes too long to reach the IRC server. This is known as lag.
Direct client to client protocol (DCC): It is used to set up a direct connection between computers. When the connection is set, files can be sent and chatting can be done directly from one computer to another by bypassing the IRC server. BY using DCC you can chat with a user privately in IRC. Advantage of DCC is that even if there is a netsplit, you can still chat with the other computer.
Chanserv: Chanserv is a program by which a user can pick channel operator for a particular channel.
Nickserv: Nickserv is a program by which a nickname can be reserved in a IRC channel for a particular duration.