Internet Relay Chat is also known as IRC. This is a system that is used for chatting involving a basic set of conventions and rules coupled with client and server software. Online, there are a number of sites like Talk City and IRC networks like the Undernet that will provide servers so that people can find and download the IRC client to their computer. Additionally, Talk City has its own IRC client applet that is downloaded for you as part of the home page, meaning that you will be able to begin chatting using an IRC connection right away.
You can create and join your very own chat group, known as a channel, or you can join an existing channel. There are protocols for discovering chat groups that already exist and the members that are in them. Depending on what type of network is being used, sometimes nicknames can be registered and thusly reserved, while other times they are only used during that particular session. Some IRC channels encourage that their members register a nickname that they will always be using. Some of them even offer up space for pictures, personal profiles, personal website links and other information that you can customize your nickname account on that channel.
There are a number of different popular IRC channels that are ongoing and provide a place for people to talk. Many IRC channels are created for websites, interests, hot topics, current events and other things that people want to converse about. You can search for channels or create your own depending on what your interests are, but it is not hard to find a channel in most cases that aligns with what you are interested in chatting about. The IRC protocol makes use of a Transmission Control Protocol, and you can use IRC via any Telnet client, typically connecting on port 6667.