John 10:11-18

11"I am the good shepherd. The good shepherd lays down his life for the sheep. 12The hired hand is not the shepherd who owns the sheep. So when he sees the wolf coming, he abandons the sheep and runs away. Then the wolf attacks the flock and scatters it. 13The man runs away because he is a hired hand and cares nothing for the sheep.
14"I am the good shepherd; I know my sheep and my sheep know me— 15just as the Father knows me and I know the Father—and I lay down my life for the sheep. 16I have other sheep that are not of this sheep pen. I must bring them also. They too will listen to my voice, and there shall be one flock and one shepherd. 17The reason my Father loves me is that I lay down my life—only to take it up again. 18No one takes it from me, but I lay it down of my own accord. I have authority to lay it down and authority to take it up again. This command I received from my Father."

The passage about being the good shepherd. I think it is important to realize the 1st century Judean context that this passage was written in. The area surrounding Jerusalem is a desert. It is dry the vast majority of the year except during the heavy rain season (which is also perilous for the sheep due to the massive flooding). There is very little if to no vegetation in most areas. The fact of the matter is, that in this landscape, without a shepherd, the flock of sheep will soon die. It isn't like American style shepherding (not that I am a shepherding expert) where there is generally a man made pond or other water source, and plenty of grass and other vegetation in which the herd just needs to be moved from time to time and cared for physically (which of course has to be done there as well).

Looking at the sheep and shepherding from this context (of which the Jesus' audience in this area would've been well aware of), we can see how much of a statement it is for Jesus to say that he is the Good Shepherd and we are his sheep. He cares for our every need, and when one of us goes lost, he longs for us and searches for us. We recognize the Christ's voice just as the sheep would recognize the voice of their shepherd calling for them.

Most of all, Christ lays down his life for his sheep. His laying down of his life for us is what saves us. In one of Peter's letters it talks about how satan prowls like a roaring lion (1 Peter 5:8), and yet we are deliverd from that prowling lion, delivered from death, and have eternal life because of our shepherd!