The Fog of War covers everything that is not within the sight range of units or buildings. When viewing the map, black areas have not yet been explored, while grayed areas have been explored but are not currently within sight range of owned or allied units or buildings. Although terrain can be seen through the grayed areas, enemy troop movements are hidden.

Take note of the Shipyard being built. The black, clouded area has never been explored so the terrain under it is not yet revealed. The grayed area between the blackness and the Shipyard has been explored, but because there are no friendly units or buildings nearby, the Fog of War prevents enemy units from being seen there.

The bright area around the Shipyard is within the sight range of that structure. Terrain there can be seen, as can enemy units (if there were any). The other brightened areas in this screen shot correspond to the sight ranges of the Town Hall and Lumber Mill. The sight ranges of units and structures are displayed when the unit or structure is selected. Catapults, Flying units and Towers have the largest sight range (9).