What is Ministry?

The spiritual work or service of any Christian or a group of Christians, especially evangelism.

Ephesians 4:11-13: 

And he gave some, apostles; and some, prophets; and some, evangelists; and some, pastors and teachers; For the perfecting of the saints, for the work of the ministry, for the edifying of the body of Christ. Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ.

Romans 10:13-15:

Whosoever shall call upon the name of the Lord shall be saved. How then shall they call on him in whom they have not believed? and how shall they believe in him of whom they have not heard? and how shall they hear without a preacher? And how shall they preach, except they be sent? as it is written, How beautiful are the feet of them that preach the gospel of peace, and bring glad tidings of good things!

Christians are to minister to others out of their devotion to Christ and their love for others, whether the other people are believers or unbelievers. Ministry to others should be impartial and unconditional, always seeking to help others as Jesus would.