The simple answer to understand about the cause of seasons in Earth is due to rotation of the Earth on its axis.
EXPLANATION:
These process is occurring throughout the year. In the following process of running an entire season, there are various parts where the ray of the sun falls directly on earth.
So, in these case the earth’s north pole is tilted over the sun, then the people living there are experiencing summer in northern hemisphere.
When the south pole is tilted over the sun, then the people living in Northern Hemisphere are having winter seasons.
