A flexible social graphing model where an actor A can follow the actor B while the actor B may or may not chose to follow the actor A. In this case A is the follower of B and B is the leader of A.
The act of following results into the follower being subscribed to the stories created by the leader. If both the actors A and B follow each other, they are also leading each other in which case they are in a mutual relationship and mutually subscribed to each other’s stories.
The Lead-Follow-Mutual (LFM) model of social graphing has been adopted by social networks such as Twitter or Instagram. It is a more flexible model than the enforced mutual social graphing where both actors A and B can only be mutually subscribed. That is because some nodes are always more popular than others and gain more followers than leaders.