Let's say you have a vector A. Let's say you draw a coordinates system. Say X,Y. By components of A we mean projections of A along the axis. Ax means the component of A in the x direction, or projection of A onto x. Similarly, for Ay.
Plane Equation thru origin: X·N = 0 for X = point on plane, N = normal to plane.
Plane Equation: X·N = d for X = point on plane, N = unit normal to plane, & d = distance to O.