First of all, we should know the basic concepts of Vanishing point that what it is.
So, the perspective projections of any set of parallel lines that are seemed or assumed that the extended finite points od 3D's meet in a point of infinity as converged but actually they are not met ina point. This is called the vanishing point.

In Computer graphics:

It permits us for creating drawings, paintings & photographs which facilitate 3dimensional looking.

By the way, in Computer graphics, the explanation will hopefully clear all confusion and that is:
"Parallel projections of an object in 3d space".
Suppose a Rubik's cube is drawn in a plane and if we extend the upper corner coordinates to forward with respect 'Z' axis perspective then the projection will look like it appears to meet a point after passes some distance though the lines were parallel. Moreover, the met point's raise is parallel to the 'Z' axis in 3D but in the real sense, it's not converged in a point. This is exactly the vanishing point.

Example (Real life example):

The railway line track raising.
More details, if look forward to railway lines, it seems that the lines are met at a point after a long distance but it's not happened since they are only parallel to move the Rail Transports. And that's the vanishing point which have some befits in computer graphics to draw and design objects that looks more real.