An autoresponder is a computer program that automatically sends an email when a prospect fills out a form on one of your landing pages. In conjunction with your account here at Online Sales Pro, your email service provider, like AWeber, for example, allows you to automatically send out emails to a group or to several different groups of people.
You will have a landing page for your product or service that gives interested customers a place to provide their names and/or email addresses. Here's an example of one:
Those names and email addresses go into a list linked with your autoresponder. Once you create the series of messages that will be sent, the autoresponder takes care of the rest, sending out the first message immediately and then the others a day or several days later - however you set it up.