Why do we have seasons?

Where most people live on Earth, in the Northern hemisphere, summers are hot and filled with many hours of strong sunlight, while winters are cold due to shortened hours of daylight and weak sunlight. Why is this? One big part of the answer is that Earth is tilted on its axis. The axis is like an imaginary stick going through the North and South poles of Earth. Earth does a complete rotation about this axis every 24 hours. 

But the axis isn’t straight up and down as Earth goes through its orbit about the Sun. Instead, the axis is tilted. Earth’s axis remains fixed in space, always pointing in the same direction, as Earth goes through its orbit around the Sun, and because it is tilted, this changes how the sunlight hits Earth at a given location. When it is summer in North America, the top part of the axis (the North pole) points in the direction of the Sun, and the Sun’s rays shine directly on North America; while in South America, where it’s winter, the axis is tipped away from the Sun and the Sun’s rays hit Earth on a slant.