Usage: TOPIC <#channel> <topic>
All users (or only channel operators if the channel has CMODE +t set) can use this command. The TOPIC command lets you change the topic of a channel.
/topic #ConferenceRoom Welcome to the Webmaster support channel.
The topic is one of the first things people see about a channel. The topic often gives some information about the channel, or highlights an amusing quote that came up in the channel recently.
The ability to use this command may be further restricted to a certain level of access in the channel, see PROP CHANNEL TOPIC and PROP CHANNEL TOPICLOCK.