This is what you think of when you think of perspective. When a scene contains straight lines (roads, buildings, boxes, the interior lines of a room) the rules of geometry dictate that those lines recede from the viewer in predictable ways. A series of objects arrayed in a line (buildings on either side of a city street, for example) will recede together toward a mutual vanishing point. If they are aligned on a flat plane, and the viewer is near the ground, then the vanishing point will be on (or very close to) the horizon. If there are different groups of objects on different lines, then there can be multiple vanishing points. If the plane is not flat (a group of buildings on the bumpy streets of San Francisco, for example) then there can be many vanishing points, some on the horizon and some not.
The effective use of linear perspective provides the eye with powerful cues about the nature of three-dimensional space in the scene. The overuse of linear perspective starts to look less like art and more like a silly stunt involving someone with a ruler and not enough to do.