Beyond removing them from your friends list, blocking triggers several other automatic changes:
Blocking, by contrast, is a digital restraining order. When you block someone on Facebook, you initiate a suite of simultaneous actions. One of the first and most definitive of these is the automatic termination of the friendship. Facebook’s system is designed such that a block overrides all previous positive connections. Therefore, You cannot block a current friend without first severing that friend tie. The system effectively says: “To block this person, you cannot be friends.” This is why, if you later unblock the person, you will find that you are not automatically friends again. The friendship is gone and must be re-established with a new friend request. if you block someone on facebook does it unfriend them