The four seasons are winter, followed by spring, then summer, and finally fall. The cycle repeats itself, however it might begin with any season and not simply winter.
Winter is the first season of the year in the Northern Hemisphere. In the Southern Hemisphere, summer marks the beginning of the new year. As the Earth rounds the sun, its tilt around its axis causes the seasons. The same principles that generate seasons also explain why the polar areas are predominantly dark during certain times of the year and predominantly bright during others. The equator experiences less seasonal change than the poles.