The vanishing point is a point at which receding parallel lines seem to meet.
The vanishing point does not always have to be in the picture, but is useful during the process of composing.
Along with the vanishing point, you must choose a horizon line, which is the apparent meeting of earth and sky. A high horizon line will focus attention on objects placed in the foreground of the landscape, since the area below the horizon will be larger than the area above it.
Because objects near the horizon line are more distant, they will appear to be smaller than foreground objects, and they will show less detail than objects in the foreground.