On the "five-fold ministry" model, pastors and teachers are two separate ministries with differing gifts and roles to play in the Body of Christ. The Greek construction of this verse, however, strongly indicates that these are two different titles for the same group, or at least, that the two groups are being considered together in this context.
Without going into actual Greek wording, we can see even in an English translation the repeated, "some to be..." construction, which occurs not five but only four times, the last time, before "pastors and teachers." What is not seen in an English translation are the articles. In English, there are two types of articles: indefinite articles ("a," "an") and definite articles ("the"). Greek has only one type of article, roughly corresponding to the English definite article, which tends to be used much more often than articles are used in English. If we were to add the articles to the passage, we would get something like this: "It was he who gave some to be the apostles, some to be the prophets, some to be the evangelists, and some to be the pastors and teachers." The one article covers both "pastors" and "teachers," strongly suggesting that they are being considered together here. There are also Greek words that form a bit of an untranslatable marker dividing the different groups (if one were to translate them, one might say, "on the one hand... on the other hand..." except that there can be as many "hands" as needed). Once again, this marker appears four times, not five, grouping the final two words together.
So is it one group with two names, or two groups that are similar enough to be thought of together in this context? I would suggest that it doesn't really matter. Those with this gift ministering in a church setting are likely to be called pastors--but as we will see, a primary responsibility of the pastor is teaching. Those with this gift ministering in an academic setting are likely to be called teachers--but a teacher should teach with a "pastor's heart"; that is, with genuine concern for the spiritual development of each student. The two aspects of the gift go hand in hand.
I have done a much more in-depth study on the biblical role of a pastor, entitled "What Is a Pastor?" (Quodlibet Online Journal 2.2). It seems clear to me that the term "pastor" is the same thing as is meant by "elder" (or "presbyter") and "overseer" (or "bishop"). As the church was beginning to coalesce and the role of apostles was increasingly less direct, terms were needed to describe leaders in the church who were not apostles. Generally speaking, "elder" came from a Jewish background--leaders among Jews were often called elders--while the Greek term translated "overseer" or "bishop" was the preferred Greek term for a leader. "Pastor" literally means "shepherd," and picks up on Jesus' frequent shepherding analogies in His teaching, as well as the Old Testament use of "shepherd" as an analogical term to describe Israelite rulers (it was also used of other Middle Eastern rulers as well), especially in Ezekiel 34, a highly instructive passage.
When one looks at the passages referring to elders, overseers/bishops, and shepherds, when used metaphorically in Jesus' teachings and in the Old Testament, a pattern emerges:
- God the Father and Jesus the Messiah are together the preeminent Shepherd/Pastor over all of the people of God; the authority of local pastors derives from this divine authority.
- The focus of the ministry of the pastor is the welfare of the sheep--that is, the people who come under the leadership of that pastor. The pastor's work is not one of self-expression or self-gratification, but rather care for the sheep.
- The conduct of the pastor is to be exemplary. Much of what the Bible discusses regarding church leadership in general has to do with godly behavioral characteristics. Pastors teach as much by how they live their lives as by what they say.
- The content of the pastor's ministry is, largely, teaching. This becomes clear as one examines the pastoral epistles and sees how many times they focus on teaching and teachers. The one major difference between the qualifications of deacons and elders or overseers in the Pastoral Epistles is that the latter group need to be "able to teach" (1 Tim. 3:2, 5:17; Tit. 1:9). A large component of this teaching ministry is protection of the people of God from false teachers (1 Tim. 1:3-7, 4:1-3). Although this protection may come partially in the attempt to silence false teaching (1 Tim. 1:3, Tit. 1:11), to a larger extent it comes as a result of patient explanation of biblical truth and drawing people's attention to topics that are important, rather than those that are spurious.
The role of the Pastor/Teacher largely comes on the heels of the other three groups: Apostles (church-planting missionaries) establish the church in a new territory, Prophets proclaim God's truth directly and draw people back to the ways of God, Evangelists (soul-winning missionaries) reach the unreached and bring them to saving faith, and Pastor/Teachers care for the Body, teaching by example and verbal instruction the truths of God's word and the right way to live. It may be that Barnabas is the best example of a Pastor/Teacher that Scripture gives us. More or less a washout on the mission field--when the going got tough, Saul, suddenly called Paul, stepped to the fore (Acts 13:6-12)--Barnabas had done his work for years previously, sticking his neck out and nurturing a former persecutor of the Church, Saul of Tarsus. Without Barnabas's patient instruction and godly example, would Paul have been able to be the foremost missionary the world has ever seen?