Perspective drawings all have vanishing points. The more you have the more difficult the drawing gets. The term orthogonal lines are a mathematical term. in this case they are the lines that get farther away from us, and later meet. Now lets talk about the number of vanishing points. If you only have one, lines (orthogonal) will go to one point on the page. However, if you have more than one, that means there will be lines going everywhere. since the lines would go in all directions, it would be harder to draw.

Here is an example of three point perspective.

https://www.thoughtco.com/vanishing-point-drawing-definition-1123080