Card recommendations are emailed to you regularly based on several different factors. They are based on:
Cards that you view
Cards that you favorited
Cards that you are the owner/author of
Cards on a playbook that you are the owner/author of
When you add or favorite a card recommendation that you received, we collect that feedback as reinforcement that the card was a helpful recommendation. When you click Not Helpful on a card recommendation, we learn from that feedback as well!