Is IRC a different chat platform than say, AIM or Google Talk, or is IRC the generic name for all chat platforms?

IRC is not a platform, but a tool, and you don’t need a proprietary client to use it.

IRC is different from both Gtalk and AIM and yes you need a client to join a channel, or you can also join some channels that have web based applets and join that way. For the Mac I’d recommend Colloquy, and I’m sure the channel that you’re trying to join has instructions if it doesn’t check this tutorial.

You do need a client, but it is not a proprietary format. Sorry.

IRC predates AIM and GTalk by a long long time. It is chat protocol, standing for Internet Relay Chat. http://en.wikipedia.org/wiki/IRC

What do I need to do to register an IRC username?

It looks like Adium supports almost everything BUT IRC.

Pidgin also handles IRC, but their site downplays Mac OS, so not sure how friendly it is. It’s free,. though, so the price to experiment is right.

http://pidgin.im/download/mac/

IRC is an application protocol. There are many different IRC networks, the most popular ones being Undernet, QuakeNet, EFnet, and DALnet. Each of these networks offer different sorts of services. For example, while some IRC networks offer Nickserv and Chanserv bots to allow you to register and reserve names and channels, other IRC networks operate on a first-come, first-serve basis.

In order to use IRC, you generally need an IRC client. (Technically this isn’t true, since if you knew the protocol well you could connect with a telnet client, but I don’t know why anyone would.) There are many, many IRC clients, the most popular being mIRC. There are, however, Java web-based clients if you search for them which will allow you to connect to various IRC networks without your own client, but you’re at the mercy of the client in terms of where you can connect and even what channels you can join.

So I register a user name when I log in to an IRC server such as QuakeNet? Do these servers have passwords?

Public IRC networks like QuakeNet will not have passwords. You just connect to their servers with an IRC client and then their welcome message should tell you what services they have available and how to access them. Most IRC clients will ask you to enter a name and an alternate name before you connect. If your first choice is already in use, it will try your alternate name. If that’s also in use, it’ll prompt you for another name. If the name you’ve chosen is registered by another user, the Nickserv bot on the IRC network will inform you of the fact and prompt you to change your name. If you don’t change your name, it will change your name whether you like it or not, usually “Guest86387” (or whatever number they’ve reached in guest names).

Thanks for the help, I got in with Colloquy, it’s working great.