This is due, for example, to the fact that when the Earth is closer to the Sun in its elliptical orbit it orbits faster, while when it is further away it orbits slower, averaging to a value equivalent to that of a circular orbit.
Earth has seasons because our planet's axis of rotation is tilted at an angle of 23.5 degrees relative to our orbital plane – the plane of Earth's orbit around the sun.
While the Earth spins through space it stays almost up right on its axis, although as it spins through space it gives us seasons. One hemisphere, when faced directly to the sun has Summer, meanwhile the other the has Winter. Later on the hemispheres have Autumn and Spring.
