Steps consist of two parts- tread and riser. Tread is the flat surface that makes up a step. It provides a smooth and safe transition between steps and landings. Riser signifies to vertical distance between each step. In simpler terms, tread is horizontal part of a step and riser is its vertical portion. Usually treads are preferred with front/longer edges profiled to bullnose, pencil edge, half bullnose, etc.