The solar system is composed of the Sun and all the objets that orbit it: planets, moons....
The larget objets are planets while the rest are moons or dwarf planets. There are eight planets, the smallest is Mercuriy which , in turns, is smaller than some moons.
Most of the solar system mass is the sun and the largest planet is Jupiter. The fourth smalles planets which are the closest to the sun (Mercury, Venus, Earth and Marts) are compact planets, made of rock and metal. On the other hand Jupiter and Saturn are mainly gasy planets composed of helium and hidrogene. The two outer planets (Uranus and Neptune) are frozen and composed of ice.
There are also asteroids, they make what has been called the asteroid belt which is between mars and Jupiter. The asteroids are , in turns of composition, alike to the four closest planets. They are made of rock and metal.
Beyond Neptune there are , what have been defined as "dwarf planets". These are not actualy planets but large enough to have their own gravity. There are thousands of them, nonetheless the largest are the asteroid Ceres , Eris and Pluto which was thought to be a planet. In addition to all of these we can also find interplanetary dust, comets and centaurs.
The solar system is located in the Orion Arm, within the Milky Way.