OAuth is a framework for access delegation. What it does is giving access to a website or a web application to get the information on another website or web application. This is how the OAuth works 1. When the user don't have account, user asks the application to login with third-party services like Facebook/LinkedIn . 2. The application asks the user get permission from Facebook/ third-party services. 3. User ask third-party application to give permission for the application. 4. Third-party application give authorization code for the application to get access to resources. 5. Using the authorization code user get the token from the third-party application. 6. By using the token application get information needed. 7. Now the user is login with the application as a valid user . Register the application To register visit to https://developers.facebook.com/ and login to it using your Facebook email and p...