Bishop and presbyter
Many words are used to describe the role of the elder, such as piloting, manager, governor; but the two main ones are episkopos and presbyteros.
Comparing Scripture with Scripture it is not hard to conclude that all these are virtually synonymous; they are used interchangeably to regulate the ministry and scope of the elders in the local assembly. In Acts 20, for instance, Paul calls for the elders and in addressing them reminds them that the Holy Spirit has made them overseers (bishops) over the church in Ephesus. In 1 Peter 5 we notice the same word-knitting: referring to the same group, Peter says they shepherd (pastor) the flock and at that same time calls them elders. In 1 Timothy 3, and Titus 1, where we have the qualifications for overseership, we find the same pattern.
However, when studying history, we sadly notice that this simple and effective pattern started to be abandoned even from the 2nd century onwards. In the Apostolic Fathers, especially Ignatius, we see a sharp distinction between the bishop and the presbyter. The bishop was seen a the one man around whom unity is to be nourished. He is assisted in the task by the presbyters, later on to be denominated priests (as the sacramental liturgy starts to strangle the vitality of the churches).
With the rise of the Antichrist, the bishop becomes the autocratic leader and administrator of the diocese, having power answerable only to the pope. Instead of nourishing and cherishing the flock, the bishop finds it natural to fleece the flock in order to maintain his extravagant life-style of "a prince of the church." Thus Diotrophes, who loved to have the pre-eminence, becomes incarnate in a thousand more. And Paul's prophecy in Acts 20, that from among the early leaders themselves, men will arise speaking perverse things and drawing disciples after them, comes true.
This sharp distinction between bishop and presbyter developed into a three-fold ministry: Bishop, priest and deacon. A hierarchy that eventually developed into something more monstrous still. Once you start importing foreign ideas into Scripture, and think that you can formulate a better form of church government than God can, where will you draw the line? The departure from the biblical pattern led inevitably to the Roman Catholic church structure, politically and administratively strong, but spiritually dead.
A return to the grass-roots is called for, even in Protestant churches. Elder, pastor, bishop, and presbyter, by sound and solid exegesis, all refer to the same person, gifted by Christ to take care of his people. We notice also that in each church (for instance, see Philippians 1:1-2), there was a plurality of elders, who, in seeking the mind of Christ, teach and disciple the people. In this, spiritual-mindedness is of the essence. Even the biblical pattern will fail miserably if the elders are self-seeking, rather that seeking to please Christ (as Timothy and Epaphrodotus were, Philippians 2).