Regular fog of war doesn't care how sight is set, it is a total black out. Even with dynamic lighting, sight, field of view, or whatever else you get as a subscriber, regular FoW totally blanks out the screen for the players. It then allows sight in only the places the DM removes the FoW. This allows a free user to somewhat have the effect of dynamic lighting by only revealing the room/hall characters are in and revealing the next bit once they open a door. The difference is that it is total manual control of what is possible to see by the DM instead of automatic with dynamic lighting.