The Solar System consists of the Sun; the eight official planets, at least three 'dwarf planets', more than 130 satellites of the planets, a large number of small bodies (the comets and asteroids), and the interplanetary medium.
Planets can be grouped by size; by position relative to the Sun; by position relative to Earth or by history. By size, the four giant planets are Jupiter, Saturn, Uranus and Neptune. To qualify as a giant, a planet must be greater than 48,000 km. The giants are sometimes referred to as gas giants. Of the eight official planets, this leaves Mercury, Venus, Earth and Mars which are known as small planets.
This subject is covered in Science at school. If you want to challenge yourself, try 500 questions on KS3 Science.