Or ask questions. Most people enjoy explaining things to you. Find spots and people you like, or create your own chatroom. Often these commands are also found in the icons of your software or its dropdown menu. All other messages you type will be seen by everybody on that channel.
Some chatrooms are private.
This means you're the Channel Operator, and thereby the 'ruler' of this channel. It still is shown in the list of channels, but it is very difficult to find out who's in it. As user of a channel you can set your usermode. Some chatrooms organize special events or meetings. An arranged time to have a party, or a conference, or what ever the chanops seem fit.