The orbitalplane of an object orbiting another is the geometrical plane in which the orbit is embedded.
Three points are required to find the orbitalplane: the center of the heavier object, the center of the orbiting object and the center of the orbiting object at some later time.
Inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit and is the angular distance of the orbitalplane from the plane of the reference (usually planets equator or the ecliptic), stated in degrees.