Let’s use a ship as an analogy. A ship has a captain and a machinist. A captain could say that a machinist doesn’t know anything about the map, water levels or anything about navigation. A machinist may know some but his efficiency may not be the same as the captain’s ability. A machinist could say that the captain does not know anything about the machine. It’s oil level, how far it can go, when it will be busted, or it’s tantrum. A captain may know something but it’s not as the same level that a machinist know about, even his eyes are close.
So how to be a manager? It is your job to know what the things that I mentioned above. Though it is acceptable not to know them all in a mastery level, because you can’t. There is no such thing as “know-it-all”. Yes, you may know it some time in your life but you can’t remember them all. So how to be a leader? It is doing the captain’s role(managerial) while working with the machinist(people). A leader can’t chart the course of the ship into it’s destination without the help of the machinist. A leader should have a technical knowledge about the ship(in/out) and machinist requirements. So that the machinist can run the machine as smooth as possible, same thing as the captain can run the ship into it’s destination. Therefore, manager and leader are two different things but cannot stand without each other.