1) A cantilever beam is a rigid structural element supported at one end and free at the other end, extending horizontally. 2) It bends downwards under loads, creating tension in the upper fibers and compression in the lower fibers. Shear force and bending moment are highest at the supported end. 3) Cantilever beams are used widely in bridges, buildings, towers, and other structures to allow overhanging elements without additional supports. Common applications include balconies, building entrances, and crane arms.