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.
Mention Mention allows to mention a member in your message and it will appear highlighted to them.
Font size Font size option allows you to change chat font size.
System message This option allows to you see or hide "user entered room" and "user left room" messages.
A random colour is chosen by default for you when you join the chat.
Middle of the page shows all the messages exchanged in the room.
Right side will show list of members who are present in that room.
Whisper After typing your message, selecting "whipser" option will send your message as a whisper.
A whisper is only visible to you and the person it was sent to.