baseboard
A strip along the bottom of a wall that protects it.
A baseboard is the strip of wood, plastic, or other material that runs along the bottom of an interior wall where it meets the floor. If you look around any room in your house, you'll probably see baseboards covering that joint between the wall and floor, usually painted white or stained to match the trim.
Baseboards serve two practical purposes. First, they protect the wall from getting kicked, bumped, or scuffed by shoes, vacuum cleaners, and furniture. Second, they hide the small gap that naturally appears where the wall meets the floor, since walls and floors rarely form a perfectly neat line. Without baseboards, you'd see an uneven crack running around the room.
In older homes, you might find elaborate baseboards with decorative grooves and designs, while newer homes often have simpler, flat baseboards. Carpenters sometimes call this trim work molding or mopboard (since mops often bump against it when cleaning floors).
When painters finish a room, they usually paint the baseboards near the end of the job. Dusting the baseboards is one of those chores that helps a room look fresh and finished.