Some Basic Terms and Ideas
A plane is a flat surface on which any two points can be chosen and connected by a line which will only go through other points on the plane. Planes are usually named with a lowercase letter. Points, lines, and segments that lie on the same plane are coplanar, and points, lines, and segments that do not lie on the same plane are noncoplanar. The point of intersection of a line and a plane is called the foot of the line. If a line intersects a plane that it does not lie on, then the intersection is exactly one point. If two planes intersect, the intersection is exactly one line.
