What Mission Is
Mission possesses several indispensable elements. It means communicating a particular message to all who will hear. It implies a style of life that gives evidence for the truth of the message. It involves going to every corner of the globe, wherever people live, to share with them the good news that the conflict and confusion caused by human self-interest has been resolved by God in an act of astonishing self-sacrifice. It implies creating new communities of people who desire to live out together the demands of being a follower of Jesus Christ and to enjoy a new life under the control of God’s rule.
J. Andrew Kirk in The Church and the World (Christian Doctrine in Historical Perspective) p.31.
I might have phrased some of this differently, but I think he’s just about hit the nail on the head.