“Nosing” generally indicates the edge of a stair tread that extends beyond the riser; it can also refer to some strip inserted to the border of a plank to provide a protective edge or a decorative appearance, or to hide timber on the edge or end. It traditionally is the leading or front edge of a piece, but the word is frequently used also to get a strip inserted on either side.
John Lum Architecture, Inc.. AIA
The dark wood of the stairs stands in stark contrast with the white wall and helps to clearly demonstrate the nosing at the edge of the tread.
The tabletop ends and here has nosing inserted to the sides.
Nosing is used to hide the advantages of plywood, rather than a strip of veneer.