The join command lets you enter a room and for java users parts them from the rooms they were in. This is the first thing you want to do when you connect to a server. You always have to place a # in front of the room name. Normally the # symbol is considered to be a part of the room's name. The example below would have you enter #webmaster. The maximum room name width is 200 characters.
Example:
/join #webmaster
Rooms are the virtual environments in which people chat. When you are in a room, you see all of the text sent to the room, as does everyone else present. While you can have private conversations with individuals who are in the same room as you are, or even with people who are elsewhere if you know their nicknames, most chat takes place in rooms. You can be in multiple rooms at the same time, but it can become confusing. Some networks may restrict the number of rooms you can be in simultaneously. It is generally best to be in a very small number of rooms that are moderately active. Java users can also look at the NEWJOIN command.