difference between ortho and perspective?

Hi first post here on BA new to blender and wondering what the differences between the 2 are and how to toggle between them?

Toggle with numpad 5

Regarding the difference between the two. Perspective is what the eye (or a camera) sees, closer objects appear larger than objects far away (projected in a cone shape). In orthographic view, everything is projected straight onto the screen (like a mechanical drawing). Perspective gives you an idea of what it looks like rendered, orthographic is good for making sure everything is lined up along a particular axis (X, Y, Z).

thanks richard!

and thezodiac thanks so much for going into detail, im just getting back into 3d and see that this site is going to be so helpful thanks for the quick responses