A designer can change the current viewpoint to a plan view of the current UCS, a previously saved UCS, or the WCS. 
A plan view is a view aimed toward the origin (0, 0, 0) from a point on the positive Z axis. 
This results in a view of the XY plane.
One can restore the view and coordinate system that is the default for most drawings by setting the UCS orientation to World and then setting the 3D view to Plan View.