The solar system consists of the Sun and eight planets orbiting it. The four inner terrestrial planets - Mercury, Venus, Earth, and Mars - are smaller and rocky. The four outer gas giant planets - Jupiter, Saturn, Uranus, and Neptune - are much larger and composed primarily of hydrogen and helium, along with icy materials. Each planet has unique characteristics and properties such as composition, size, distance from the Sun, and atmospheric composition that distinguish it from the others.