And Jesus came and said to them, "All authority in heaven and on earth has been given to me. Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you. And behold, I am with you always, to the end of the age."
Matthew 28:18-20

Mission is engaging in God’s plan to redeem the world by extending his kingdom into every race, language and nation. 

The emphasis of missions is on those with whom you would not have ordinary contact. In other words, mission is cross-cultural. A humble, loving, confident witness meets people’s needs while living the gospel story. So the goal of mission is evangelism, but the means is compassion. Social concern and evangelism are not mutually exclusive. They are intricately linked together.

If you are growing in Christ and receiving the benefits of God’s blessing, sooner or later God will give you a burden for those who are not saved. There are between 2.5 and 3 billion people in the world who have not heard the claims of Jesus Christ. Thousands of distinct groupings of people which are scattered throughout the world have not even heard the gospel. They are called “unreached people groups.”

Paul shares his passion for mission to unreached people

In Romans 10:14–15: “How, then, can they call on the one they have not believed in? And how can they believe in the one of whom they have not heard? And how can they hear without someone preaching to them? And how can they preach unless they are sent? As it is written, ‘How beautiful are the feet of those who bring good news!’ ” Just as with Paul, discipleship causes Christians to identify with God’s plan for the world. And that leads to action.[1]

[1]Jeffrey Arnold and Stephanie Black, The Big Book on Small Groups (Downers Grove, Ill.: InterVarsity Press, 1997).