In this video, we will understand what are parallel projections in Computer Graphics. 
Parallel projections are generally used by engineers and architects for creating working drawing of the object. If they want complete representations of any object, they consider two or more views of an object using different planes. Parallel projections help in displaying the picture in its true shape and size. 

Types of Parallel Projections: 
1) Orthographic Projection 
2) Oblique Projection 

Orthographic projection: In orthographic projection object along with parallel lines is perpendicular to the view plane. In the orthographic projection front, side, and rear positions are called elevations. The top is called the plan view. 
It is again classified into 2 types those are: 
1) Multiview Projection 
2) Axonometric Projection 

Oblique projection: It is a kind of parallel projection, where projecting rays emerges parallelly from the surface of the polygon and incident angle is not perpendicular to the view plane. 
It is again classified into 2 types: 
1) Cavalier 
2) Cabinet 

Parallel Projection in Computer Graphics
https://www.geeksforgeeks.org/parallel-othographic-oblique-projection-in-computer-graphics//