The vanishing point, relates to perspective. The vanishing point of a drawing, painting or photo can be seen where all lines intersect on the horizon line.

The most common example that is taught to explain a vanishing point is to imagine straight train tracks going off into the distance; at their smallest width as seen by the eye, this is the vanishing point.

When drawing an object that requires perspective, referencing straight lights to one or even two vanishing points allows the artist to acheive corrent perspective of the object as it would be seen at any conseivable angle.