This is the use of an email Software or Autoresponder to distribute promotional messages, newsletters and free bonuses to your subscribers. Basically, you can send your visitors something that is interesting, hoping that it will entice them to buy from you.

Having your subscribers email addresses on your Autoresponder software make it easy to send them messages from time to time. Also, you could make them trust you by also giving them free and valuable information too, this way they will feel you are out to help them and not just to make them buy products repeatedly.