When an email recipient performs a desired action based on a mailing you have sent. A conversion could be a monetary transaction, such as a purchase made after clicking a link. It could also include a voluntary act such as registering at a Web site, downloading a white paper, signing up for a Web seminar or opting in to an email newsletter.

The 3 Things To Avoid When Emailing Your List
When you decide to have an opt-in list, it is not just a matter of sending your subscribers your promotional newsletters or catalogs.