Simply put, planets in the solar system revolve around the sun and the solar system is held together by its own gravitational field. The solar system consists of nine planets, the sun, each planet's moons, comets, asteroids and meteors.
The earth rotates around the sun and as it does so, it creates day and night. All other planets rotate around the sun as well, although at different rates. Mercury, for example, orbits the sun in 88 days because it is closer than any other planet. Jupiter, the largest planet in the solar system, takes 4,331,572 days to orbit the sun.