A reflector is a passive component that reflects light back. There are various forms of reflectors, which are used in lights for light shaping or as retro-reflectors in reflectors, for example.
Reflectors for light shaping.
For light shaping (see beam pattern), a reflective shape is constructed around a light source (lamp or LED). This has the effect that the light is no longer emitted in all directions, but can be used, for example, as a strongly bundled spot.
Retroreflectors consist of small cells of three mirrors, each at a 90-degree angle to the other. This design ensures that light hitting the reflector is not diffused but reflected directly back to the light source. Retroreflectors are therefore very well perceived in the dark.
An alternative to retroreflectors are so-called cat’s eyes. These consist of a converging lens and a reflective surface at the focal point of the lens.