Earth has seasons because it is tilted by 23.5º. Earth’s axis is always pointed in the same direction, so it changes the orientation and angles between the Earth and the Sun, and different parts of Earth get the Sun’s direct rays throughout the year. The tilt affects how long the days are how low or high the sun rises in the sky. Winter Solstice is the day when we in the northern hemisphere will be tilted farthest away from the sun.
Watch this video to learn how you can use sticks and stones to watch the earth move around the sun, and mark the important dates like the solstice.