We describe the physical basis of Jet Vapor Deposition (JVD), in which sonic, inert gas "jets in low vacuum" are used as vapor sources for depositing films. A "multiple jet, moving substrate" strategy enables deposition of a wide variety of multicomponent, multilayer and "host-guest" materials generated from metals, semiconductors, and dielectrics. We show how jet structure, behavior, and vapor transport underlie advantages of JVD such as high rate deposition and flexibility in multicomponent synthesis.