In the course Authentication & Authorization: OAuth on Udacity, you will learn about the difference between authentication and authorization. You will also explore how OAuth 2.0 simplifies the implementation of security for developers and users. Through the use of Google's OAuth 2.0 Playground, you will witness OAuth 2.0 in action while making API requests. Additionally, you will discover how to create a Google+ Sign-In for your web application, understanding the various security flows that can be implemented and how security can be managed by both the server and the user's browser. Furthermore, you will learn how to add a permission system to your application using Python code, allowing you to limit database access for each logged-in user based on your code design. You will also add a User model to your database to store credentials obtained from the OAuth provider's API. Lastly, you will gain the knowledge to add multiple OAuth providers to your web application, including implementing Facebook Login as an alternative sign-in option for your users. The course will teach you how to utilize OAuth provider documentation to add any number of providers as desired.