Part elements in Revit support the construction modeling process by letting you divide certain elements from the design intent model into discrete parts.
Video: Create and Divide Parts
These parts, and any smaller parts derived from them, can be independently scheduled, tagged, filtered, and exported. Parts can be used by construction modelers to plan delivery and installation of pieces of more complex Revit elements.
The elements you create parts from can be in the current project or in a linked model.
Parts are automatically updated and regenerated when the original element from which they are derived is modified. Such edits might include adding/removing layers, or changing wall type, layer thickness, wall orientation, geometry, materials, or openings.
Concrete parts possess rebar cover and can host rebar, rebar sets, area reinforcement, path reinforcement, and fabric reinforcement.
Deleting the original element from which parts have been derived will delete all those parts as well as any parts derived from them. However, deleting a part or parts will reveal the original element.
Copying the original element from which parts have been derived will copy all the associated parts as well.