the sun is a kind of star & the earth revolves around the sun ->  the earth revolves around a star  the moon orbits the earth & earth is a kind of planet ->  the moon orbits a planet  the moon orbits a planet & revolving around means orbiting ->  the moon revolves around a planet  the earth revolves around a star & the moon revolves around a planet -> the difference between the earth and the moon is that the moon revolves around a planet