What is the term for the wall that forms the exterior skin of a building?

A curtain wall is the term used to describe the exterior skin of a building. This type of wall is non-structural and primarily serves to protect the interior of the building from environmental elements such as wind and rain. It also allows for design flexibility, as it can be made of various materials like glass, metal, or stone. Unlike load-bearing walls, which support structural elements of a building, curtain walls are not responsible for structural stability; rather, they are affixed to the building's frame and can enhance aesthetic appeal while promoting energy efficiency through insulation and glazing technologies. This distinction is important for understanding modern architectural practices and fire safety considerations, where the materials and construction techniques of exterior walls significantly impact fire resistance and spread.