Providing authentication and authorization is necessary for web applications. We'll discuss authentication and authorization in this section. The new paradigm that has evolved over the past few years is OAuth. We'll learn about and use OAuth 2.0 for implementation. OAuth is an open authorization mechanism, implemented in every major web application. Web applications can access each other's data by implementing the OAuth standard. It has become the most popular way to authenticate oneself for various web applications.
For example, on https://www.quora.com/, you can register and log in using your Google, Twitter, or Facebook login IDs. It is also more user-friendly, as client applications (for example, https://www.quora.com/) don't need to store the user's passwords. The end user does not need to remember any more user IDs...