It is the upper protective system of a building, designed to shield it from the elements (rain, snow, wind, sun). It consists of multiple layers, including the structural base, a waterproof layer (underlayment), and the main visible material (such as asphalt shingles, metal, or clay tiles). It also incorporates ventilation systems and metal flashing to prevent leaks. It is fundamental to the structural integrity, energy efficiency, and aesthetics of any building.