What is virtual fog?

Answer 1

Fog (of war) was often used in games that could not afford to render things in the distance; everything over render depth was usually obscured by a blurry wall -- it just happened to work out as a useful gameplay element.

Sometimes gray/whiteout blurring is also used to indicate unexplored areas of a map.

Do you mean a different kind?

Answer 2

does this concept have any importance in IoT