What is a Principle Orthographic view?

An orthographic drawing is one that uses a sort of perspective that does not portray an object the way it would look in a natural space. It shows each side of the object as flat and parallel to the "picture plane." It's not too unlike cubism. (Braque and Picasso explored drawing people and object by showing all sides at once.)

This is used in order to give accurate engineering/mathematical dimensions. It is used for the fabrication of mechanical parts, furniture...