OAuth is an authentication protocol that allows users to register with your web application using an external provider, without the need to input their username and password. OAuth is mainly used by social platforms, such as Facebook, Twitter, and Google, to allow users to register with other websites using their social account.
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To learn more about how OAuth works, visit the OAuth protocol website at http://oauth.net/.
Passport supports the basic OAuth strategy, which enables you to implement any OAuth-based authentication. However, it also supports user authentication through major OAuth providers using wrapper strategies that help you avoid the need to implement a complex mechanism by yourself. In this section, we'll review the top OAuth providers and how to implement their Passport authentication strategy.