Planes are flat, two-dimensional surfaces that can be defined by three points. To create a plane, connect two points by a straight (infinite) line. Pick another point that is not included in that line. Draw a second line that contains this third point and intersects the first line. Label the intersection as your origin (0,0). Move an infinitesimal distance along each axis and connect those two points. Continue this in all four directions, progressively moving outwards. You now have a plane.