If you want a friend to join your channel you can invite him. This is required if your channel is 'invite only'. Well, you guessed it, if there is a way to invite someone on a channel, there is also the ablility to KICK someone out of it. For example ,if a person is behaving in an offensive manner by annoying people or flooding the channel with unwanted information, they can be forced out of the channel. Only 'channel operators' are privileged to use this command.
Channels have topics, that indicate the current topic of conversation.
At times, you may want to send a description of what you are doing or how you are feeling or just anything concerning you on the current channel or in a query.