Planets are the members of the Solar System. They look like stars but they do not have light of their own. They reflect the sunlight that fall on them. They keep changing their positions with respect to the stars. A planet revolves around the Sun in a definite path. This path is called an orbit. The time taken by a planet to complete one revolution is called its period of revolution. As the distance of the planet increases from the Sun, the period of revolution increases. A planet also rotates on its axis besides revolving around the Sun. The time taken by the planet to complete one rotation is called its period of rotation. Some planets have moons or satellites revolving around them.