Earth revolves around the Sun in an elliptical orbit with the Sun at one of the focii. The path is almost like a circle , as the eccentricity is very small.
The Earth takes 365.25 days to revolve around the Sun once. The central force of attraction supplies the centripetal force for Earth to be in the orbit. The distance of Sun from Earth is around 150 million km.
When the Earth is close to Sun, during the summer, it revolves faster (moves faster) and moves slower during the winter and is farther away from the Sun.
T² = 4π² R³ / G M
T is the time period of revolution. R is distance of earth from sun.
G gravitational constant. M is mass of Sun.