Vapour chambers are designed spread heat very efficiently, they conduct heat up to 25 times better than plan copper.
They work much like a flattened out heat pipe, they are a sealed vacuum, containing a small amount of working liquid, the liquid is normally water or alcohol, being in a vacuum lowers the boiling point of the working liquid, to a point that boils at very low temperatures. Heat for the processor or GPU heats the vapour chamber the working liquid boils and evaporates fill the vapour chamber, it then cools on the cold side the vapour chamber and returns to it's liquid form, and working liquid wicks back to the hot side of the vapour chamber to repeat the process.

Internal structure of vapour chamber.
Vapour chambers are used where there is a need to effectively spread out heat, from a small heat source to larger surface where it can be more effectively cooled. They have been used on graphics cards for years, as the offer a very compact way of spreading a lot of heat, and also low profile server heatsinks for the same reason.
They are now being used on desktop CPU heatsinks to solve the issue of decreasing die size. Despite there name integrated heatspreaders on modern CPUs aren't very good at spreading heat, the heat from the CPU Die is focus in the center of the heatspreader , this causes an issue for your typical heatpipe cooler, because only the center most heatpipes end up dissipating most of the heat from the CPU, while the outer heat pipes do very little.
By placing a vapour chamber on the bottom of a heatsink between the CPU and the heatpipes, the vapour chamber can spread the heat from the center of the CPU evenly across all the heatpipes, making the heatsink much more effective.
oops just noticed the date of the original post, my bad.