The Solar System consists of the Sun,  9 planets -  Mercury,  Venus,  Earth,  Mars,  Saturn,  Jupiter,  Neptune,  Uranus,  Pluto,  63 planetary satellites and a large number of small bodies (comets and asteroids).

The inner solar system consists of the Sun, Mercury, Venus, Earth and Mars.
The outer solar system consists of Jupiter, Saturn, Uranus, Neptune and Pluto.

ORBIT
The orbits of the planets are ellipses, though apart from Mercury and Pluto they are very nearly circular.  The planets all orbit in the same direction, anti-clockwise if you were looking down from above the Sun's north pole.  All the planets apart from Venus and Uranus rotate in that  direction as well.

RELATIVE SIZE
To try to understand the relative sizes of the planets, imagine the Sun being 1.50 metres in diameter, then the Earth would be a mere 1.3cm in diameter, Jupiter would be 15cm, Saturn about 8cm.

CLASSIFICATION
Mercury, Venus, Earth and Mars can be thought of as the rocky planets.  These planets are composed mainly of rock and metal, rotate slowly, have solid surfaces, rotate slowly and have few satellites.
Jupiter, Saturn, Uranus and Neptune  are usually described as gas planets. These planets are made up mostly of hydrogen and helium, rotate at high speed, have deep atmospheres, rings and lots of satellites.

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