Planets are classified by their size, composition, and position relative to the Sun and Earth
terrestrial or rocky planets: Mercury, Venus, Earth, and Mars:
The terrestrial planets are composed primarily of rock and metal and have relatively high densities, slow rotation, solid surfaces, no rings and few satellites.
jovian or gasplanets:
Jupiter, Saturn, Uranus, and Neptune:
The gas planets are composed primarily of hydrogen and helium and generally have low densities, rapid rotation, deep atmospheres, rings and lots of satellites.
inner planets: Mercury, Venus, Earth and Mars.
outer planets: Jupiter, Saturn, Uranus, Neptune.
The asteroid belt between Mars and Jupiter forms the boundary between the inner solar system and the outer solar system.
small planets: Mercury, Venus, Earth, Mars.
The small planets have diameters less than 13000 km.
giant planets: Jupiter, Saturn, Uranus and Neptune.
The giant planets have diameters greater than 48000 km.
The giant planets are sometimes also referred to as gas giants.
inferior planets: Mercury and Venus.
closer to the Sun than Earth.
The inferior planets show phases like the Moon's when viewed from Earth.
Earth.
superior planets: Mars thru Neptune.
farther from the Sun than Earth.
The superior planets always appear full or nearly so.