Each planet in the Solar System is unique, but they share certain qualities.
All, of course, orbit the Sun, caught in its gravitational force. All are solid or partially solid and reflect light. All but two—Mercury and Venus—have at least one satellite, or moon, of their own.
To our knowledge, none—other than Earth—has any life forms. We call the first four terrestrial planets because they share many earthlike qualities. The next four are known as Jovian planets, because they are like the planet Jupiter. (Jove is another name for Jupiter.)
Jovian planets—also called gas giants—have small solid centers, but huge, thick layers of gases. Pluto is like no other planet. The planets closer to the Sun than Earth are also called the inferior planets.
Those farther from the Sun than Earth, including Pluto, are called the superior planets.
The relative sizes of the Sun and the planets in our solar system. Jupiter is the largest planet. Pluto is the smallest planet, smaller even than the Moon.