Using Auth0 in your applications means that you will be "outsourcing" the authentication process to a centralized login page in the same way that Gmail, YouTube, and any other Google property redirects to accounts.google.com whenever a user signs in.
Your user will authenticate, and Auth0 will generate an ID Token and Access Token that will be passed back to your application. The Access Token can then be used to call your API and extract attributes for that user (such as name, email, role, or a custom attribute)
When your app needs to fetch user data from your API:
For server-side web apps, Auth0 uses the Authorization Code Flow.
The easiest way to implement the Authorization Code Flow is to follow our Regular Web App Quickstarts.
Or, to use our API endpoints, you can follow our tutorial: Call Your API Using the Authorization Code Flow.
Step-by-step instructions for tasks
Understand the fundamentals