They will be able to see your public posts, comments on mutual friends' public photos, and your tags in old photos.
However, while there is no direct notification, the person may still figure it out through indirect clues. Below is a report on how unblocking works and the ways a user might realize they have been unblocked. 1. Indirect Ways They Might Notice
They will regain the ability to tag you in photos or posts and invite you to events or groups. Important Consequences of Unblocking