Why does most of an RF current flow within a very thin layer under the conductor's surface?

The concentration of RF current just beneath the surface of a conductor is defined as the skin effect. The rapidly alternating current induces internal magnetic fields and eddy currents that oppose the main current flow in the center of the wire, forcing the moving electrons out toward the thin surface layer. While self-inductance plays a role in creating the opposing magnetic fields, "skin effect" is the specific and universally accepted term for this exact surface-flow phenomenon. Distractors mentioning decreased RF resistance or interior heating are fundamentally incorrect, as the skin effect actually increases the effective resistance of the wire by reducing the cross-sectional area available for current flow.