One Point Perspective
The front plane of the object is directly in front of you, verticals parallel, and all lines of perspective meet at a single vanishing point on the horizon.
Two Point Perspective
When an object or viewpoint is rotated and two sides of an object are angled away from your view, each side of the object has it's own unique lines of perspective. These now use two vanishing points, one for each plane of the surface in view with the vertical lines parallel.
Three Point Perspective
This is where observations higher or lower a third vanishing point comes into use. It is like looking up at tall skyscrapers and seeing three vertical sides angle to a third vanishing point, far distant, as they reach toward the sky. From the Worm’s Eye view (looking up) the upper vanishing point is called the Zenith. From the Bird’s Eye or Helicopter view (looking down) the lower vanishing point is called the Nadir.