The purchase, Catch All Contacts, will look back in time (1 or 5 years back) to see what contacts you have missed so that you can add them to your Contacts list. This is a one time purchase for this account.
The existing feature, Discover New Contacts, will find contact information for new people from the current time moving forward. If you are a Premium subscriber, these new contacts will be added for you. If you have a basic (free) EasilyDo account, you can add the contacts one-by-one from your EasilyDo feed.