Lamps are illuminants for energy conversion with the purpose of illumination. They differ in the type of light generation. Known lamp types are halogen lamps (low voltage, high voltage), compact fluorescent lamps and LED lamps. Furthermore, arc lamps or metal halide lamps are also available. Lampholders are integrated into luminaires for inserting and replacing lamps. The lamp base, e.g. with Edison thread (incandescent lamps), pin base (car direction indicators) or socket base (licence plate lighting) is screwed or pressed into the respective lampholder, thus establishing the power connection. Screw sockets for lamps with Edison threads (E27, E17) and GU sockets (fluorescent lamps, low-voltage halogen lamps) are the most common variants. Depending on the model, locking devices are available, for example to ensure trouble-free operation of car headlights. In addition to their use in buildings and vehicles, lamps are used in a wide variety of applications. Colloquially, there is often no clear distinction between socket and base.