This document provides definitions of key terms related to our solar system. It defines planets, stars, the inner and outer planets, orbits, rotation, revolution, comets, gas giants, satellites, space probes, asteroids, and phases of the moon. The document distinguishes between inner planets Mercury, Venus, Earth, and Mars and outer planets Jupiter, Saturn, Uranus, Neptune, and Pluto. It also defines important concepts such as a planet's axis, its orbit around the sun or another object, and the spinning and revolving movements of objects in space.