It is an FAA-U.S. thing.
It is the point where, descending to, or level at, MDA, you would intercept a hypothetical ~3° glide slope (since it is for non-precision approaches, there is no "real" glide slope to track.)
Marked on plates with a heavy bold
V symbol.
http://images.slideplayer.com/14/433...s/slide_57.jpg
Basic idea is to avoid pilots flying to the MAP and getting "visual" with the runway environment at the last moment and making a steep descent. The VDP will normally be reached before the MAP.