Non metallic flexible conduits are usually made of PVC with corrugated appearance. A wide variety of communications cables, optical fibers and other low voltage cables.
Depending on the type, it may be ultraviolet resistant for outdoor use, or suitable for burial. Because it's usually made of a solid material, it's waterproof, but it's resistant to chemicals and corrosive.
Non metallic flexible pipes are used in riser applications, HVAC, water treatment systems, and many other applications.