Why was teaching in parable the best way for Jesus to get his message across?

The use of parables was a change in Jesus' way of teaching in Matthew 13 v10 the disciples ask why he uses parables to teach. Jesus' reply is that parables are an effective method of revealing truth to the spiritual and the ready mind

A parable is a story to illustrate a truth ,in order to explain it, to make the truth easier to understand.

A parable puts something familiar alongside something unfamiliar. It compares something unfamiliar with something familiar.

A parable is similar to a fable or an allegory or a proverb except parables are generally concerned with spiritual matters

A parable helps people to understand spiritual truth by using everyday objects and relationships.

In New Testament times parables were a common way of teaching.