The Whisper feature lets you send short private messages to someone in the same room as you. Unlike the Popup PM and Offline Message systems, the recipient does not have to be your friend to be able to receive/reply to your messages.
There are two ways you can use the whisper feature, the first by right-clicking the name of the user in the room list, and the other using the generic /whisper command.
If however, you are trying to send more than a few lines of text or chat with someone you are connected to, use the Offline Messages system or PM system instead. You will need to 'Friend' them first.
Whisper to User
Turn on Whisper mode with a user by Right-Clicking a username and selecting Whisper On.
This turns on whisper mode with that user until you turn it off. Any further messages you type in chat will be seen by just that user and you. The message text will be prefixed by ">> username" to indicate messages you type are going to that user. You will also notice the "Whisper On" has changed to "Whisper Off" for that user's menu.
Once done talking to the user, you can go back to talking in the room by clicking "Whisper Off".
The quick whisper feature allows you to send one whisper at a time to someone in the room. The normal text size limit of chat applies to whisper messages too. You cannot send a whisper to someone not in the current room.
Help Tip: Instead of typing the recipient's username by hand, you can click the name in chat to copy their name into your text. Usernames are not case-sensitive.
Command syntax : /whisper <username> <text>
As always post any questions you may have in the comments below. Happy Broadcasting!!