When your attendees sign up for an event, you can create a custom message that they will receive upon the completion of their registration. From the event page, you will go to Media & Communications, then Email Confirmations. You can include anything you would like in these confirmations; most people include a thank you note for registering, any pertinent information they will need prior to your event, and maybe even a coupon code if they refer a friend.
You can also create a custom confirmation for your exhibitor registrants than have been approved. Once you create your confirmation, it will also include the organization's name, packages purchased, booth assignments, and a link to view their confirmation and assign registration tickets.