PVP (polyvinylpyrrolidone) is a yellowish synthetic resin.
It’s a polymer - a large molecule made of repeating units (monomers).
It forms a thin film over the hair, preventing absorption of moisture.
It gives our hair gels extra styling power. It is said to be anti-irritant, too.
In cosmetics and skincare, it is a binder and coating agent to control viscosity of a product.
Citrus fruits are sometimes coated with PVP.