The word pastor comes from a Latin word which means “shepherd.” The New Testament presents two offices that constitute church leadership—elder/overseer and deacon. Paul lists the qualifications for elder/overseer in 1 Timothy 3:1–7 and Titus 1:5–9. Notice that in the 1 Timothy passage, Paul refers to them as overseers/bishop (episcopos in the Greek), and in Titus he refers to them as elders (presbuteros in Greek). From this it can be concluded that there is one office with different designations. The word elder refers to the life experience of the office holder, while the word overseer/bishop emphasizes the responsibility of the office holder to watch over the congregation and meet their spiritual needs.
The second office is that of deacon, which is described in Acts 6:1–6. Paul outlines the qualifications of deacons in 1 Timothy 3:8–13. The deacon’s responsibility is to minister to the physical needs of the congregation, freeing up the elders to concentrate on their spiritual needs. In Acts 20:28, Paul said to the Ephesian elders, "Take heed therefore unto yourselves, and to all the flock, over the which the Holy Ghost hath made you overseers, to feed the church of God, which he hath purchased with his own blood."
Notice that Paul is telling the elders (office) to be shepherds (function or role) over the church.
In Ephesians 4:11, Paul identifies shepherding “pastors” as one function in the Church along with teaching, missionary work, evangelism, and prophecy. That this role is important is seen by the emphasis that Jesus puts on it in John 21:15–17 where Jesus charges Peter to feed and tend His sheep.
How is a pastor/shepherd supposed to feed and tend the flock of God? He does this by being able to teach the flock the word of God (1 Timothy 3:2; Titus 1:9) to bring the flock into maturity, and to be resistant to heresy. He is on guard for false teachers and warns those who stray that there are consequences to their belief and behavior.
In the New Testament, the words pastor, elder, and overseer can be used interchangeably, with each word providing a different emphasis on what contribution the leaders make to the Body of Christ. The three words come together in 1 Peter 5:1–2 where Peter exhorts elders to shepherd the flock of God and serve as overseers, caring for the flock as they wait for the Chief Shepherd.