A parable is an illustration using either a story, something seen, or something known to teach a lesson. Illustrations stay with us longer and so Jesus used illustrations to teach the people about God the Father, about the Kingdom of Heaven and even to teach us something about Himself. Much more can be learned from these parables than can be written here, but you should find this web site contains many links to information that can help you dig deeper into these parables and their meanings.
Jesus wanted us to know what God was really like. He wanted us to know what kind of character God has. By studying these parables we can come to know our Creator better and come to love Him more. (To understand this purpose of Jesus better read Teaching in Parables.)
In the days when Jesus was on the earth, there were some who really wanted to know the truths that He taught. These people understood what Jesus was saying. There were others that were not interested in knowing truth, but were looking for something that they could use against Him. These spies did not understand what was being said and so Jesus was also protecting Himself until the time of His death was close. In fact, many of the parables that Jesus spoke were given in the last 6 months before He died on the cross. (See the Ministry of Jesus Timeline.)
13:10 And the disciples came, and said unto him, Why speakest thou unto them in parables?
13:11 He answered and said unto them, Because it is given unto you to know the mysteries of the kingdom of heaven, but to them it is not given.
13:12 For whosoever hath, to him shall be given, and he shall have more abundance: but whosoever hath not, from him shall be taken away even that he hath.
13:13 Therefore speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand.
13:14 And in them is fulfilled the prophecy of Esaias, which saith, By hearing ye shall hear, and shall not understand; and seeing ye shall see, and shall not perceive:
Here is a list of parables Jesus used while trying to teach us about our Father: