Pastors are to oversee the church.They are fathers of the church to make sure the sheep of God are well fed(word of God), well clothed (garment of righteousness)and so on.I don't mean teachers , apostles prophets and evangelists aren't responsible for these!Of course they are,but pastors are to oversee almost everything concerning the sheep.
A simple explanation can be put this way;
Evangelist/Apostle goes somewhere and preaches the gospel.People receives Jesus as their personal savior. Then teachers are on duty to teach them how to live Christian life,the life that pleases God.Pastor is in charge to see everything concerning the sheep and their welfare is smooth. I mean if two couples have problem with their marriage,Pastor is supposed to know first!Elders are just pastors assisting pastor.Prophet is there to correct the church,and sometimes Brings special messages from God.I'm not talking about spiritual gifts but rather the 5 ministry Jesus gave on Eph4
This is from my understanding from the Bible

-------You Love Jesus? Serve Him!--------