Exodus 19:1-2,9-11,16-20; Daniel 3:52-56; Matthew 13:10-17
In this interlude between speaking to the people, Matthew has Jesus explaining his methods to his apostles. Clearly, He is happy that they do understand his message (do they?). But they do not understand why Jesus does not simply say in plain words what his message is.
Partly the reason is cultural - most teachers of that time used similar techniques. The old testament is absolutely full of examples. But Jesus would not simply do what every other teacher was doing - he was distinctive. In the text in the translation we are used to He speaks in parables, but other biblical scholars (e.g. Nicholas King) use the word 'images'. I feel this more accurately describes what Jesus was doing. Parables suggest a desire to obscure, to make deliberately difficult, the message. Jesus is however painting images of situations that his audience would understand, so as to allow his message to emerge with a little observation and time spent looking.
The Ignition way of reading the bible makes use of this technique: allow His words to paint an image in your mind: some people actually get a pencil and paper and sketch what Jesus says. Or find an image by an artist relevant to the story.
Then just look at it for a while. The meaning that you need to see today, will emerge.
Just to help us a little, in the following verses, Jesus explains the image of the sower to his disciples - read Matthew 13: 18-23 (this is the Gospel for tomorrow).