A ceiling covers the upper interior surface of a room and conceals the structure above. Ceilings can be decorated and come in different materials and designs. The document discusses various ceiling types including coffered, barrel vault, tray, suspended, glass, metal, beam, wooden, gypsum, POP, and acoustic ceilings. It provides examples of each type and notes their advantages such as cost-effectiveness, ease of installation, sound control, and ability to incorporate lighting and ductwork.