The animation below shows how shadows change during the day in the northern hemisphere. Shadows are created when an object, such as the stick below, blocks out some of the Sun's light. The length of the resulting shadow depends on how low or high the Sun is in the sky.
Here's a practical suggestion:
The next time it's a sunny day, go outside and have a good look at your own shadow. If it's midday then you will cast a shorter shadow than if it's late afternoon or early morning - just like in the above animation.