Question

what causes seasons on Earth

Answer 1

it depends on the tilted position of earth on its axis and also the part which is towards the sun which causes winter or summer solstice

Answer 2

The seasons are caused by the tilt of the Earth's rotational axis away or toward the sun as it travels through its year-long path around the sun. The Earth has a tilt of 23.5 degrees relative to the "ecliptic plane" (the imaginary surface formed by it's almost-cicular path around the sun).