Here's why:

* Earth's Tilt: The Earth is tilted on its axis at approximately 23.5 degrees. This tilt causes different parts of the Earth to receive more direct sunlight at different times of the year, leading to seasons.

* Changing View: As the Earth orbits the Sun, our perspective of the night sky changes. Imagine looking at a distant object while walking in a circle. Your perspective of that object shifts depending on where you are in your circle. Similarly, as the Earth moves in its orbit, our viewpoint of the stars changes throughout the year.

* Different Stars Visible: This changing perspective means that different constellations are visible in the night sky at different times of the year. Constellations we see in the summer are not visible in the winter because they are on the opposite side of the Earth during those times.

Think of it like this: if you stand in a field and look at the horizon, you can only see part of the field. As you walk around the field, you see different parts of it. The constellations are like the different parts of the field, and our journey around the Sun is like walking around the field, revealing different sections of the night sky.