Here is an easy to understand animation that explains the science of Earth’s seasons. The video above illustrates the Northern hemisphere, and the one below, the Soutern hemisphere.
From Dr James O’Donoghue:
The length of time we’re exposed to Sun each day, combined with the Sun’s angle in the sky (high angles = high intensities), lead to the seasons. My aim here was to make a visual of this fundamental concept in a single frame. Hope this helps you understand seasons in a new way.