We have different seasons because the earth is tilted.
As the earth moves around the sun, some parts are tilted towards the sun and receive more sunlight, which causes the temperature to rise. This is summer.
The parts which are tilted away receive less sunlight, making it cooler. This is winter.
As the earth continues its orbit, the tilt remains the same but now the regions receiving sunlight change, and that’s why the seasons change.
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