Jesus spoke many parables while He was on earth because much of the wisdom that He tried to impart was just to complex for the people to understand. A parable is a way of using earthly examples to explain a Heavenly principle so that it could be understood, and when reading the Bible we see that Jesus used this pattern many times.
In John 10, we read about the Good Shepard. We see that the Lord uses a familiar idea in that culture: shepards and their flocks. As you probably know, sheep have a way of knowing their master, and will follow him only, even when multiple folks are brought together. This happened often at night, when in the courtyard of a home a gatekeeper ("porter") was hired to keep all of the sheep in a pen while the shepard's slept.
On my father's dairy farm growing up, we did not have sheep, but the cows did follow his voice when it came time to calling them down from the hillside for feeding. They knew him, and he knew them - even if one of the 80 were missing. Same with sheep, and also the same with God - He knows us and is calling out to us so that we might choose to follow Him.
Let's look at the entire portion of Scripture now:
John 10:1-18 (KJV)
Verily, verily, I say unto you, He that entereth not by the door into the sheepfold, but climbeth up some other way, the same is a thief and a robber.
But he that entereth in by the door is the shepherd of the sheep.
To him the porter openeth; and the sheep hear his voice: and he calleth his own sheep by name, and leadeth them out.
And when he putteth forth his own sheep, he goeth before them, and the sheep follow him: for they know his voice.
And a stranger will they not follow, but will flee from him: for they know not the voice of strangers.
This parable spake Jesus unto them: but they understood not what things they were which he spake unto them.
Then said Jesus unto them again, Verily, verily, I say unto you, I am the door of the sheep.
All that ever came before me are thieves and robbers: but the sheep did not hear them.
I am the door: by me if any man enter in, he shall be saved, and shall go in and out, and find pasture.
The thief cometh not, but for to steal, and to kill, and to destroy: I am come that they might have life, and that they might have it more abundantly.
I am the good shepherd: the good shepherd giveth his life for the sheep.
But he that is an hireling, and not the shepherd, whose own the sheep are not, seeth the wolf coming, and leaveth the sheep, and fleeth: and the wolf catcheth them, and scattereth the sheep.
The hireling fleeth, because he is an hireling, and careth not for the sheep.
I am the good shepherd, and know my sheep, and am known of mine.
As the Father knoweth me, even so know I the Father: and I lay down my life for the sheep.
And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd.
Therefore doth my Father love me, because I lay down my life, that I might take it again.
No man taketh it from me, but I lay it down of myself. I have power to lay it down, and I have power to take it again. This commandment have I received of my Father.
Jesus starts out this parable stating, "Verily, verily" and again echos this phase in verse 7. Remember that in Scripture key ideas are repeated again and again, and when Jesus says "verifly" He is in essence saying "this is the truth." The sheep here are just like us humans in that we are dependent on our Creator (even if we don't know it), and the sheep fold is the Church (remember, this is not only specific to a "congregation" because the Bible makes clear that an individual believer in Jesus is the Church.
It is interesting to me that verses 1-5 of this parable is directed towards those in ministry; at the time it was for the Pharisees and now can be looked at for those looking to enter into the pastorate (the only way is through Jesus Christ). Jesus points out that His flock will only follow Him and His words, not those of a stranger. God has given us not only His Word, the Bible, but also the Holy Spirit to test those things that we see and hear in order to prove if they are of God or not.
Verse 6 shows that those listening to Jesus still didn't get what he was trying to say. There are times when I do not fully understand what the Bible tells me, but through prayer and studying God makes His way known to me. I need to be patient and commit to seeking after Him. Jesus gets his audience's attention again by clearly stating that "I am the door of the sheep." In my own house, the front door offers an opportunity for fellowship as friends and family may enter in to share in my life, but also security and protection. Jesus makes clear that this is the same with those who trust in Him, and that the Holy Spirit that is available to us now will help us to see what ideas or actions are of God or man.
Verses 9-11 explain more of the ultimate sacrifice that Jesus was to make for me, and you, and all those who live in this fallen world. He saved us from death, and offers today a way of salvation by the forgiveness of sins
because of His death, burial, and resurrection; we can have eternal life! So much in this world continues to point towards the way of death and separation from God, but in His infinite love He offers a life that is more abundant than any of the perceived riches we can obtain on this earth.
We go on to read about a difference between someone hired to watch the flock and its owner in verses 12-14. On the farm of my youth, my dad could not care for every aspect of the lives of his cows. There was milking twice daily, feeding and cleaning, as well as going out to gather hay and plant corn. He needed to hire people to help him, and when my siblings and I were old enough we were assigned duties to assist my dad. We cared for the responsibilities that he gave us, but not to the full expectations that he had. His care was greater because he had a bigger stake than just helping - he was responsible for everything. Same with me at work in the pharmacy: at the end of the day everything to do with the business is on me (from proper filling and dispensing of medicines to recording the refrigerator temperatures). I have people to help me, but in the end it is my responsibility to be sure every task is completed properly. Jesus is the good shepard, and will not flee from us in times of trouble - Charles Stanley refers to Him as our "anchor in times of storm." He was, is, and will be here with us. He knows us and cares for us.
The parable concludes with Jesus again foreshadowing his death on the cross for His people, even those that were not Jewish. Remember that Jesus' earthly ministry was focused towards offering salvation to his people, the nation Israel. On the cross, he was mocked as the "King of the Jews" and yet endured the pain of our sins our of obedience to the plan that God had for him. He came to be our living sacrifice (John 15:13) and make a way for the Gentiles (like me - I am in the fold of vs 16 that He speaks of) to be offered the forgiveness of sins by His act of love for us.
God knows us, and He loves us. Jesus Christ, the Son of God, came to this earth to fulfill all of the requirements of the Hebrew law, and offer a way of salvation from the death of sin for those who believe in Him. It is not by works, but from faith in what He did. That is caring that is out of this world!