sic:tldr:5357f

This command is likely used in a messaging service or chat client.

The command begins with a colon (:) which is often used to indicate a command in messaging platforms.

"j" is a command syntax used to join or enter a particular channel or chat room.

"#${channel}" is a placeholder that represents the name or identifier of the channel you want to join. The use of "#" suggests that it is a channel rather than a direct message or private conversation.

"" represents pressing the Enter or Return key on the keyboard to execute the command.

Overall, this command allows a user to join or enter a specific channel in a messaging service by typing the name or identifier of the channel and pressing Enter.