IRC gained international fame during the late Persian Gulf War, where updates from around the world came accross the wire, and most people on irc gathered on a single channel to hear these reports.
Servers exist to pass messages from user to user over the irc network.
Please only use the latter when you have no other way of reaching irc, as this resource is quite limited. It's usually best to try and connect to one geographically close, even though that may not be the best. You can always ask when you get on irc. It's probably best to take a look around and see what you want to do first. A Channel Operator is someone who has control over a specific channel.