What is the purpose of stair tread nosing and how does it enhance the safety and durability of staircases?

Stair tread nosing is the rounded edge of a stair step that extends slightly over the riser below. It helps improve safety by providing better visibility of the edge of the step, reducing the risk of tripping. Additionally, the nosing protects the edge of the step from wear and tear, increasing the durability of the staircase.