Think about a surface and two points on that surface. This surface is only a plane if the line segment connecting the two points, which we talked about earlier, lies completely on that surface. A plane can be described in a unique way if any of the following are true. If it has three points that don't all go in the same direction. If the plane is perpendicular to a given vector and goes through a point, then it is a straight line. If you know the distance and normal of a plane with respect to the Origin point, you can figure out its shape. The Normal form is the name for this type of plane.