The object is able to reveal areas of the map within his sight radius, revealing Shroud of Darkness and Fog of War.
BRIEF DESCRIPTION :: Line of Sight. The distance that the unit can see in any direction. Shroud of Darkness and Fog of War is lifted within range of a unit's LOS.
Only units and structures have line of sight (with most structures having minimal vision radius, other than tall structures like towers and fortresses).
BRIEF DESCRIPTION :: When the object is re-covered with Fog of War, the viewer's last image of the object is retained until the object is again revealed.
Typically used for enemy buildings, since they aren't likely to move around. Also for Gaia objects (so the player can recall the location of trees, rocks, and so forth).
BRIEF DESCRIPTION :: The unit is invisible to certain kinds of units.
If an entity does not have this attribute, it is assumed that the entity is visible to any player, ally, enemy or even Gaia. If we want to specify that it is only visible to certain allegiances, however, we can specify it here.
BRIEF DESCRIPTION :: Any stealthed entities within LOS (for example, those concealed in forests) will be visible to the player.
If the player is sharing vision with his allies, then they will also be able to see the revealed units.