5 OAuth essentials for API access control

Auth’s Roots in the Social Web
OAuth puts the user in control of delegating access to an API. This
allows one service to integrate with another service on behalf of
that user. The same social Web providers who popularized the
pattern of exposing an API to enable third-party developers to
enrich their platforms were the first ones to apply such delegated
authorization mechanisms. OAuth was defined in 2006, to
standardize mechanisms of this kind.