Alright, let's get started with managing user authentication. First things first, create a Firebase project. Head over to the Firebase Console, click on "Add project", type in a project name, and accept the terms. Easy peasy.

Now, on your project dashboard, you'll see an option to "Add Firebase to your web app". Click on that. You'll get some configuration settings—copy those. You'll need them when you initialize Firebase in your app.

Time to install the Firebase SDK. If you're using npm, just run npm install --save firebase. If npm isn't your thing, you can include the Firebase CDN in your HTML like this:

<script src="https://www.gstatic.com/firebasejs/5.10.1/firebase-app.js"></script>
<script src="https://www.gstatic.com/firebasejs/5.10.1/firebase-auth.js"></script>

Next up, initialize Firebase in your app using those configuration settings you copied earlier:

var config = {
apiKey: "<API_KEY>",
authDomain: "<PROJECT_ID>.firebaseapp.com",
databaseURL: "https://<DATABASE_NAME>.firebaseio.com",
storageBucket: "<BUCKET>.appspot.com",
};
firebase.initializeApp(config);

Head back to your Firebase project settings, go to the "Authentication" section, and enable the sign-in methods you want. Firebase supports a bunch of options like passwords, phone numbers, and popular providers like Google, Facebook, and Twitter.

Now, let's authenticate your users using the Firebase Authentication API. For example, to sign in a user with email and password, use firebase.auth().signInWithEmailAndPassword(email, password). Firebase also supports social sign-ins with .signInWithPopup() or .signInWithRedirect().

To keep track of user states, set up a listener for Firebase's onAuthStateChanged event. This event triggers whenever the user signs in or out. Use it to manage the user's session and provide context for their authentication state across your app's components.

For user authorization, use Firebase's Realtime Database or Firestore Database Security Rules. These rules check the user's token and permissions before allowing them to access or modify data. Define rules based on the user's role or access level to cover all scenarios where your data can be read or written.

Protect your app routes or pages based on user roles or states. Use the user's authentication state and the onAuthStateChanged event listener to set up conditionally rendered routes.

Finally, make sure you provide a way for users to sign out. Just call Firebase's signOut function: firebase.auth().signOut(). This ensures that when the user logs out, their session is cleared and the authentication state is updated across your app.