Orbital inclination

Fig. 1: One view of inclination i (green) and other orbital parameters

Orbital inclination is a term that says that there is an angle between two planes. It is often used to describe the movemet of celstal bodies such as stars and planets. In that context, an inclination of 0 degrees means the orbiting body orbits the planet in its equatorial plane, in the same direction as the planet rotates.