To distinct between perspective & parallel projection, the characteristics concepts of both will assist us. Since the perspective projection is also categorized into 3 points & parallel projection is categorized into orthographic and oblique parallel projection.

However, the main separation of perspective & parallel projection is mentioned here as the priority by which we can clarify our concepts about projections in Computer Graphics:
1. Perspective projection creates a realistic image/picture of an object whereas Parallel projection does not form a realistic view of an object.

2. Perspective projection is located as a finite point on the contrary Parallel projection is located at infinite points.

3. In perspective projection, the Projector is not parallel on the other hand in parallel projection Projector is parallel.

4. The perspective projection represents the object or picture in 3 dimensional way but the parallel projection represents in different ways (For example Telescope, military projection, etc).

5. For displaying the accurate view of object the perspective projection isn't perfect but with the help of Parallel projection, the object can be viewed more accurately.

6. To generate natural images the perspective projection is used by "Artists" whereas "Drafters & Engineers" uses Parallel projection to draw pictures or objects.

The above are the main distinctions between Perspective & Parallel projection and tried to mention more precisely.