An airdeck is just that. It is a "high" pressure inflatable deck that supports weight and provides structure and rigidity to the boat. They're not highly regarded in larger SIBs, - eg over 3.5m
They are constructed from two sheets of material, interconnected with lots of tiny drop stitches that hold it all together. They are very light and actually work very well.
They generally have an inflatable keel below them to push down and form a bit of a vee in the water.
I was very impressed with mine, not having expected much....