In strategy games, there is a fog over areas where you have no vision (ie places you dont have any units that can see exactly what is happening at that moment).

In strategy games, there is a fog over areas where you have no vision (ie places you dont have any units that can see exactly what is happening at that moment). This introduces uncertainty and allows for more strategy based on positioning and vision. This is based on a real military concept: http://en.wikipedia.org/wiki/Fog_of_war http://en.wikipedia.org/wiki/Fog_of_war