A vapour chamber consists of a sealed vacuum vessel mostly made of copper with an internal wick structure and a small amount of working fluid.

Usually, copper powder is sintered to the inner wall of the vessel.
The low pressure inside the chamber allows the liquid to evaporate at a temperature far below its average boiling temperature.

When the vapour comes into contact with a cooler wall surface, it condenses and releases its latent heat of vaporization.
The condensed liquid returns to the heat source through the capillary action of the wick structure.