Use this tag when the perspective of a picture appears to draw the viewer's eye towards a central point. An example might be a city street as seen from the center of the road.
It is possible for an image to contain multiple vanishing points, especially if you're viewing a scene from an angle. See, e.g. post #1312088.
This is an artistic technique, so don't bother with images with a photo background unless it's a major focus of the image. One can assume nature gets it right.
