Example of differing sight areas.
Fog of War, also known as FoW, is a gameplay mechanic which limits all player's sights. Players cannot see locations they have not been to, thus preventing them from easily spying on enemies and from knowing exactly when the enemies are attacking. This makes the gameplay deeper and richer.
Engines[]
In the original Glest game, you can turn Fog of War (and Shroud of Darkness with it) off in the INI. In GAE and MegaGlest, this can be done on the new game screen.