The four seasons are winter, followed by spring, which is followed by summer and then autumn. After autumn comes another winter, and the cycle repeats although it can begin with any season, not just winter.
In the Northern Hemisphere, the first season of the year is winter. In the Southern Hemisphere, the new year begins with the summer season. The seasons are caused by the tilt of the Earth around its axis as it orbits the sun. The same properties that cause seasons also explain why the polar regions are mostly dark for parts of the year and mostly light for other parts. There is less variation in the seasons at the equator than at the poles.