Matthew 28:18-20 (New International Version)
18 Then Jesus came to them and said, “All authority in heaven and on earth has been given to me. 19 Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, 20 and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age.”
“The Greek term typically translated as “servant” or “minister” (diakonos) is found extensively throughout the New Testament. It can be used both subjectively and objectively to describe a person functioning in an intermediary capacity or to describe an act itself (i.e., “a servant” or “a service”). It is also used as a verb to express the act of ministering or serving. A survey of these uses of “ministry” and “service” (diakonos) in the New Testament reveals several aspects of the biblical nature of ministry.
First, ministry is personal. That is to say, ministry does not exist detached and independent of the person (or people) ministering and receiving the ministry. Luke describes how, at around the age of 30, Jesus began “his ministry.” Paul speaks of how he himself received a ministry from Christ Acts 20:24. Beyond this, Ephesians 4:12 describes how all the members of the Body of Christ are equipped for service or ministry for the sake of the community. Thus, we cannot escape the fact that ministry is personal and, in some sense, conferred upon people by God.
Second, ministry is interpersonal. Ministry does not flow uniformly from subject to object; Paul does not only minister to the churches of the New Testament, but receives ministry from them as well Romans 1:12. Scripture consistently relates the notion that ministry involves interaction. This is emphasized by the simple fact that “ministry” and “service” are translations of the same Greek term. To minister is to serve another, as evidenced in Matthew 23:11: “… but the greatest among you shall be your servant.”
Third, while ministry involves people, the content or purpose of ministry is the communication (in word and deed) of the gospel 2 Corinthians 9:13, Colossians 1:23, 1 Peter 4:10. Just as Christ has reconciled us to himself, we also have the “ministry of reconciliation” 2 Corinthians 5:18, where God uses us to reconcile the world to himself through Christ. Naturally this may include a host of different ministries, but the point to emphasize, as Paul does in 1 Corinthians 12:5, is that “there are varieties of ministries, but the same Lord.” Therefore, amid the diversity of people ministering, the content of ministry centers upon the gospel of Jesus Christ and everything that message entails.
Fourth, ministry is hard work. We know Christ’s ministry was not warmly received by everyone, and neither was Paul’s, for that matter 2 Corinthians 11:23. This is why Paul implores Timothy to fulfill his ministry even in the face of hardships 2 Timothy 4:5. If the ministries of Christ, Paul, and others were demanding, why should we expect anything different in our ministries? To be sure, ministry can be joyful, but we should not mistake this joy for the absence of hardship 2 Corinthians 4:1.”
http://www.collidemagazine.com/article/244/a-biblical-definition-of-ministry-in-a-technological-age