The Planets in Orbit

Here is an animation of the first 4 planets in orbit around the Sun. The distances from the Sun and orbit times are to scale. The actual orbits are slightly elliptical.

All the planets, except Pluto, orbit the Sun in more or less the same plane called the ecliptic plane, so viewed from Earth they appear to move in a band, close to the ecliptic, called the zodiac.

Pluto's orbital plane it tilted by about 13 degrees to the others.

Retrograde Motion
Viewed from Earth Mars appears here to stop (stationary point), move backwards (retrograde motion), stop again (another stationary point) and then continue normally. Of course Mars doesn't move backwards it just appears to when the Earth and Mars are in certain positions.

There are a number of other terms which we need to know. (in the pictures below the Sun is the big yellow one and the Earth is blue)

Greatest Elongation	Conjunction	Opposition	Transit	Occultation
The greatest angular separation of an inferior planet (Venus 450 or Mercury 280) from the Sun.	When 2 or more planets appear close to each other in the sky. Here the two inferior planets are in conjunction.	When a superior planet (Mars, Jupiter, Saturn etc) lies directly on the other side of the Earth to the Sun.	When a smaller body passes in front of a larger one. Mercury and Venus may, at times, pass in front of the Sun	When a smaller body passes behind a larger body and so is hidden, e.g. when a planet passes behind the Sun.