Imail (also known as Messaging) is what you do to communicate with other members besides using the forums and chat. Imail is a 1 on 1 chat with another member. You can find out if you have a new imail by either going to the News link on the right or looking to see if the Imail link has '1 new' or however many imails there are next to it.
Your inbox lists all messages you have received. Here you can select numerous imails and delete them, or you can just leave them in there, beware though that there is a limit to the number of imail you can hold in both your Inbox and Sentbox.
There is a compose form at the bottom of the imail page on whatever imail or box you are in. In the first text box you must enter the member's ID number, in the second box you should enter the subject of your message, and finally in the biggest box you can type out your message to send. Once ready to send your message you can click the button with the text 'Send' within it.
This box has the imails you have sent to other members, this does count towards the imail limit, so be wise in the ones you choose to keep. Saving your sent messages is turned on by default.
The imail limit for members is 60, however if you are a VIP member then you are able to hold 120 imail's.
With Imail you can read a message, make a new message, reply to a message, or delete a message.