Learn how to implement user login and registration in a React.js application using Auth0 in this comprehensive tutorial. Create an Auth0 account and app, install the necessary npm package, set up environment variables, and implement the Auth0Provider context. Develop login and logout buttons, create a profile component, and handle Auth0 loading and error states. Follow step-by-step instructions to integrate a secure authentication system into your React app, and gain insights into the pros and cons of using Auth0 for user management.