Reflection probe
A point in the scene that captures its surroundings as a cubemap, letting glossy surfaces reflect the room without re-rendering the world per surface.
True reflections mean drawing the scene from every surface — hopeless in real time. A reflection probe does the work once: it renders the surroundings to a cubemap from its position, and shaders then sample that map for every glossy surface nearby. A car's paint picks up the garage around it almost for free.
It is the cousin of the light probe, but for mirrored rather than diffuse light. Most probes are baked (static), though modern engines refresh some in real time. The error shows when an object strays far from the probe and the reflection no longer matches where it stands.