You can invoke a virtual action to go along with your conversation. You talk on IRC simply by typing a message, and make an action by typing /me followed by a description of the action, as in:
/me looks at his watch
This will produce a sentence on the channel that starts with your nickname, so that it will read “yourname action”, like the following:
John looks at his watch
Since your action begins with your name, many people phrase the action so that it reads well with a name as the first word.
/me waves to everyone else.
You can also ascribe actions to other people with the /describe command, as long as you use a valid nickname of someone currently on the network.
/describe Steve slaps his forehead
This will produce a sentence on the channel as though someone else has performed an action.
Steve slaps his forehead