Effective calling is an act of God the Father, speaking through the human proclamation of the gospel, in which he summons people to himself in such a way that they respond in saving faith.
Wayne Grudem, Sytematic Theology, p.693
In distinction from effective calling, which is entirely an act of God, we may talk about the gospel call in general which comes through human speech. This gospel call is offered to all people, even those who do not accept it. Sometimes this gospel call is referred to as external calling or general calling. By contrast, the effective calling of God that actually brings about a willing response from the person who hears it is sometimes called internal calling. The gospel call is general and external and often rejected, while the effective call is particular, internal, and always effective.
ibid.