Seasonal variation on earth is due to the

Distance of earth from the sun at any given time
Elliptical path the sun takes around the earth
Revolution of earth on its axis
Tilt of the earth’s axis of rotation

The seasonal variation on Earth is primarily due to the tilt of the Earth's axis of rotation. This tilt causes different parts of the Earth to receive varying amounts of sunlight throughout the year as the Earth orbits around the sun. When one hemisphere is tilted towards the sun, it experiences summer, while the other hemisphere is experiencing winter. As the Earth continues its orbit, the tilt causes the seasons to change. The distance of Earth from the sun at any given time and the elliptical path the sun takes around the Earth also play a role in the variation of sunlight intensity, but the tilt of the Earth's axis is the main factor determining the seasons.