Have you ever been doing a little online shopping, then hop over to check your email and notice those ads on the side promoting the thing you were just searching for? That's called Retargeting.
Retargeting is an online advertising method that allows you to push ads out specifically to visitors to your website once they leave your site. By tracking the pages they visit within your site, you are able to push ads out to them, custom to their interests. For instance, if they were on your mortgage page, you could populate home buying ads for them. Perhaps another person visited your membership page - populate an ad about online membership enrollment.
Since you have already established a lead with your website visitors, retargeting is a great way to use that knowledge and try to establish a new account or expand the services your members are utilizing!