In the picture on the right, you can see that the Earth "tilts" towards the Sun by around 23°. This is called the Axial Tilt of the Earth. The "poles" sticking out of top and bottom of the Earth are not real of course; they are just there to show you the axis points around which the Earth spins - known as the North and South Poles.
However, the North Pole does not always tilt towards the Sun, but gradually moves right around during one year (i.e. one orbit), so for half of the time the North Pole is pointing away from the Sun and the South Pole is pointing towards it.
Try this animation to see what we mean.
You can see this in the picture below. When the North Pole is pointed towards the Sun, it is Summer in the Northern Hemisphere. When it is pointed away from the Sun, it is Winter.
To carry out a short experiment to see why the tilt of the Earth makes it hotter in the Summer and colder in the Winter, click here.
Why not look at the following two demonstrations, which will help to reinforce your knowledge of the Seasons: