They are generally made from composites like fiberglass and carbon, as are surf skis. Their narrow beam makes them tippy, but climb back on and keep at it. The key distinction between the tourer and the wave and surf ski is an ability to carry gear, either in a closed hatch or depression in the hull. Most also are at home on an ocean wave. They're fairly maneuverable and fast, but not especially well suited for overnight trips.
Weight is the finished weight of the craft from the manufacturer.
See the Materials explanation on page XX for a detailed explanation. Target weight range for the boat designated by the manufacturer to achieve optimum performance. Manufacturer's suggested retail price.