The Solar System contains the Sun, eight planets with their moons, and lots of other smaller objects such as dwarf planets, asteroids and comets. The distances between planets in the solar system are huge so we use a unit of measurement based on the average distance from Earth to the Sun, called an astronomical unit (AU).
The four planets closest to the Sun are called the inner planets and are typically small, warm, rocky worlds, that have few (or no) moons and no ring systems. They are: Mercury, Venus, Earth and Mars.
The four outer planets are much larger and cooler, and mainly made of gas. They all have a lot of moons and ring systems, although we can only see Saturn’s rings from Earth. Also known as gas giants, they are: Jupiter, Saturn, Uranus and Neptune.