Mention Mention allows to mention a member in your message and it will appear highlighted to them.
Whisper After typing your message, selecting "whipser" option will send your message as a whisper.
Right side will show list of members who are present in that room.
Clicking a members names in the right side list will show the "user options" as shown in the image above and each option is explained below.
Other Rest of the menu show some basic information about that member.