shroud VS FOW is game specific terminology - many games using what you call 'shroud', use the term 'FOW' for it. In general terms, FOW just means youve got imperfect, inaccurate or conflicting information about or communication across the arena.
Shroud would be more accurate.
Fog of War does not regrow, whereas shroud goes.
Yeah, I always thought FOW is the one that regrows while Shroud is the one that goes away once you explored the map.
Wiki has mixes the two terms: http://en.wikipedia.org/wiki/Fog_of_war#Simulations_and_games