What are the three different categories …

Earth and the other three inner planets of our solar system (Mercury, Venus and Mars) are made of rock, containing common minerals like feldspars and metals like magnesium and aluminum. So is Pluto. The other planets are not solid. Jupiter, for instance, is made up mostly of trapped helium, hydrogen, and water. There are four main categories of classifications when determining the type of celestial body an object is. These classifications are: terrestrial planets (Mercury, Venus, Earth, and Mars), gas giants (Jupiter and Saturn), ice giants (Uranus and Neptune), and dwarf planets (Pluto, Eris, Haumea, and Makemake). The planets of the solar system are grouped into three categories, based on their size and composition: They are gas giants (2), ice giants (2), and terrestrial planets (4 – including Earth).