Seasons are created by the angle of the sun compared to the angle of the earth. The earth is on a 23.5 degree angle. This means that some part of the earth is always closer to the sun. This happens as the earth is orbiting round the sun. Another main reason is that the North pole always points in the same direction. This means that when it is summer in the northern hemisphere the North Pole is facing the sun. When it is winter in the northern hemisphere the North Pole is facing away from the sun. Another fact is the the North Pole is on an angle so it is never exactly pointing at the
sun.