Earth spins around its axis at an angle of 23 degrees. This means that as Earth orbits the sun, different parts of the planet get more or less exposure to the sun. The tilt of the Earth is responsible for the seasons, climate, and weather. Part of the "Orbit: Earth's Extraordinary Journey" series.
The entire three part series is fantastic work. While it is lengthy to try and show all three parts to students, we have found part 3, focusing on the Earth's tilt to be a great piece to share with students studying Earth's seasons.