This lamp cap is a component of an incandescent lamp. An incandescent lamp generates light by heating a tungsten filament until it glows inside a glass bulb filled with an inert gas to prevent oxidation. When electricity passes through the filament, it emits light through incandescence. Known for its warm light, incandescent lamps have been widely used since the 19th century but are less energy-efficient than LEDs and CFLs, leading to their decline in favor of more efficient lighting options.