Have you ever looked down railroad tracks and noticed that the far ends look much smaller than the ends nearer to you, and the gaps between the rails seem to narrow until the lines become one, just as they disappear over the horizon? This is because perspective helps you, the artist, to understand an object's location in relation to where you are and it helps you make your drawing of an object look more realistic. It is an important concept in industrial design and architecture.
perspective: the illusion of depth on a two-dimensional surface
The Two-Point Perspective
You've already learned the basic way of drawing a perspective. On a new sheet of paper, draw again your horizon line, but this time - add two vanishing points, each of which is opposite to one another ( imagine drawing a segmented line ). Now, draw the lines outward from these two vanishing points and add vertical lines to make your cube. You will notice that the vertical lines appear to be parallel. You will feel like you are looking up at the top half and bottom half of the cube.
Like in one point perspective, you can make the object appear to be on top by just drawing lines above the horizontal line. This comes handy when you are drawing any flying objects like jets.
If you want to draw an aerial view or a " bird's eye view " - you may just draw anything below the horizon line to create an impression of looking down at it.