A view-specific 2D drafting element in Revit that fills a sketched boundary with a hatch or solid pattern - used for annotation, not for real building geometry. A filled region only exists in the view it was drawn in - it has no real-world thickness or 3D presence - which makes it the right tool for things like poché, paving patterns on a plan, or a highlighted zone that shouldn't affect quantities or schedules the way an actual model element would.