Open Authorization
Open Authorization, sometimes called OAuth, is an open standard for access allocation, usually used as a method for Internet users to give websites or applications access to their information on different websites but without providing them with the passwords. This method is used by some companies such as Amazon, Google, Facebook, Microsoft and Twitter to allow the users to share their account information with third parties, such as applications or websites.
OpenID
OpenID is an open standard and decentralized authentication protocol in which a user can create their own account by selecting an open ID identity provider, then after that, this account can be used to sign onto other websites. It allows users to be authenticated by co-operating sites using a third-party service, eliminating the need for webmasters to provide their own ad hoc login systems.