A parable is a simple story illustrating a moral or religious lesson. Sometimes, spiritual things are difficult to understand so a parable may be used to help us understand by telling us an earthly story. We can transfer the meaning of the parable to the spiritual truth that the parable is speaking of.
Parables were also used in scripture to hide spiritual things from those who refuse to put their trust in Christ.
You need to be careful not to make doctrine out of a parable. A parable is used to reveal or to help us to understand a spiritual truth and not to declare it.
Sometimes, people read facts in the Bible, but that don't want to accept those facts, they say that it is a parable. Usually, a parable will be identified as a parable, and it will never use a person's name in it. Parables will also be explained in scripture as to their meaning.