A DEFINITION

Peter ties elder (presbuteros) together with Shepherd when he refers to Jesus as the chief shepherd (archi-poimen) He calls himself an elder. Note that Jesus clearly delineated his calling as "Feed my sheep" in John 21:16-17

1 Peter 5:1 The elders which are among you I exhort, who am also an elder, and a witness of the sufferings of Christ, and also a partaker of the glory that shall be revealed: 2 Feed the flock of God which is among you, taking the oversight thereof, not by constraint, but willingly; not for filthy lucre, but of a ready mind; 3 Neither as being lords over God's heritage, but being examples to the flock. 4 And when the chief Shepherd shall appear, ye shall receive a crown of glory that fadeth not away.

Shepherd
It is a word naturally of frequent occurence in Scripture. Sometimes the word "pastor" is used instead Jer 2:8 3:15 10:21 12:10 17:16 This word is used figuratively to represent the relation of rulers to their subjects and of God to his people Ps 23:1 80:1 Isa 40:11 44:28 Jer 25:34,35 Na 3:18 Joh 10:11,14 Heb 13:20 1Pe 2:25 5:4 The duties of a shepherd in an unenclosed country like Palestine were very onerous. "In early morning he led forth the flock from the fold, marching at its head to the spot where they were to be pastured. Here he watched them all day, taking care that none of the sheep strayed, and if any for a time eluded his watch and wandered away from the rest, seeking diligently till he found and brought it back. In those lands sheep require to be supplied regularly with water, and the shepherd for this purpose has to guide them either to some running stream or to wells dug in the wilderness and furnished with troughs. At night he brought the flock home to the fold, counting them as they passed under the rod at the door to assure himself that none were missing. Nor did his labours always end with sunset. Often he had to guard the fold through the dark hours from the attack of wild beasts, or the wily attempts of the prowling thief (see) 1Sa 17:34.