A planet is a body that revolves around a star that is enormous enough to be spherical by its own magnitude, is not huge enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The word planet is an ancient word which ties to history, astrology, science, mythology, and religion. Five planets in the Solar System are seen with our naked eye. These were observed by many early cultures as celestial, or as emissaries of idols. As logical knowledge advanced, human awareness of the planets changed, incorporating several dissimilar objects. in our solar system, we have eight planets they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.Planets are mostly divided into two main types: big low-density giant planets, and smaller stony terrestrials. There are eight planets in the Solar System. In order of rising distance from the Sun, they are Mercury, Venus, Earth, and Mars, then the four giant planets, Jupiter, Saturn, Uranus, and Neptune. Six of the planets are circled by one or more natural satellites.Numerous thousands of planets around other stars ('extrasolar planets' or 'exoplanets') have been shown in the Milky Way. As of 5 Feb 2019, 3,956 known extrasolar planets in 2,973 planetary systems (plus 654 multiple planetary systems), going in size from just above the size of the Moon to gas goliaths about twice as large as Jupiter have been discovered, out of which more than 100 planets are of the same size as Earth, nine of which are at the same comparative distance from their star as Earth from the Sun, i.e. in the circumstellar habitable area.