Role

A part, or character, performed by an actor in a drama; hence, a part of function taken or assumed by any one; as, he has now taken the role of philanthropist.

what something is used for; "the function of an auger is to bore holes"; "ballet is beautiful but what use is it?"

the actions and activities assigned to or required or expected of a person or group; "the function of a teacher"; "the government must do its part"; "play its role"