JOIN <#channel> [key]

The JOIN command allows you to enter a public chat area known as
a channel. Network wide channels are proceeded by a '#', while
a local server channel is proceeded by an '&'. More than one
channel may be specified, separated with commas (no spaces).

If the channel has a key set, the 2nd argument must be
given to enter. This allows channels to be password protected.

See also: part, list
