OAuth is an open protocol to allow secure API authorization in desktop, mobile and web applications. “OAuth is a simple way to publish and interact with protected data. It's also a safer and more secure way for people to give you access. ... OAuth allows you to share your private resources (photos, videos, contact list, bank accounts) stored on one site with another site without having to hand out your username and password.” OAuth.net, retrieved 12:40, 23 April 2009 (UTC).
The need for protocols like OAuth is increasing in order to make use of webpage or desktop widgets easier. In other words, in the cloudcomputing sphere, OAuth is to programs what OpenId is to users.
See also: OpenID the related "Web 2.0" protocol for user identity and authentication management.