Earth has four seasons. They are summer, fall, winter, and spring. The Earth moves around the sun. One trip takes a year. As it moves, the Earth is tilted. This is what causes the seasons.
The equator is an imaginary line around Earth’s middle. Do you live above the equator? In the summer, this part of the Earth tilts toward the sun. It is warmer. In the winter, this part of the planet tilts away from the sun. It is colder.
It is the opposite for people who live below the equator. When it is winter there, it is summer above the equator.