Concerning the role of the pastor, the Bible says a great deal. The primary terms that describe the role of the pastor are “elder,” “bishop,” and “teacher” (1 Timothy 3:1-13). “Elder,” or episkopos (from which we get our word episcopal) refers to the oversight of the believers, and it involves teaching, preaching, caring, and exercising authority where needed. The elder also serves in the church as leader and teacher. In Titus 1:5-9, Paul urges Titus to "appoint elders in every city." They will teach and lead the congregation in their spiritual development. Also, in 1 Peter 5:1-4, Peter addresses his "fellow elders" and tells them to "be shepherds of God’s flock that is under your care, serving as overseers—not because you must, but because you are willing, as God wants you to be; not greedy for money, but eager to serve" (v. 2).
So concerning the role of senior pastor the Bible doesn’t address that title specifically. It has come into existence as the church has grown and required additional staff. The title of senior pastor refers to the person who primarily leads the church, generally doing the majority of the preaching and teaching in the pulpit at the services and overseeing the administration of the church. Some larger churches may even have an executive pastor who oversees the day-to-day operation of the church, while the senior pastor then would be responsible for working with the church board, along with the preaching, teaching, and counseling ministries that go with the role of pastor.
Every church, whether large or small, needs a pastor who will shepherd, lead, feed, and guide the people to spiritual growth and service for the Lord Jesus. In larger churches, a senior pastor often shepherds the pastoral team in addition to shepherding the congregation. As a result, a senior pastor should be held to an even higher standard of agreement to 1 Timothy 3:1-13 and Titus 1:6-9 than other pastoral roles.