1. Introduction

This tutorial aims to provide a comprehensive understanding of Firebase Authentication and Firestore Database. Firebase Authentication provides backend services to help authenticate users, and Firestore is a flexible, scalable database for mobile, web, and server development.

By the end of this tutorial, you will be able to:

• Understand and implement Firebase Authentication.
• Create, read, update, and delete data in Firestore Database.
• Apply security rules to protect your data.

Prerequisites

Basic knowledge of JavaScript and any JavaScript framework (like React, Angular, Vue, etc) would be beneficial.

2. Step-by-Step Guide

Firebase Authentication

Firebase Authentication provides easy-to-use services for authentication. It supports authentication using passwords, phone numbers, popular federated identity providers like Google, Facebook, and Twitter, etc.

To use Firebase Authentication, you need to:

1. Create a Firebase project and add Firebase to your app.
2. Enable the sign-in method you want to use.
3. Implement user sign-in/sign-up flow in your app.

Firestore Database

Firestore is a NoSQL database to store and sync data between your app users in realtime. Firestore's data model revolves around documents (which are key-value stores) and collections (which are containers for documents).

To use Firestore Database, you need to:

1. Set up Firestore in Firebase console.
2. Start a new collection.
3. Add data to the collection.

3. Code Examples

Firebase Authentication

Here's a code snippet for signing in a user with email and password:

const auth = firebase.auth();

auth.signInWithEmailAndPassword(email, password)
  .then((userCredential) => {
    // Signed in 
    var user = userCredential.user;
    // ...
  })
  .catch((error) => {
    var errorCode = error.code;
    var errorMessage = error.message;
    // ...
  });

Firestore Database

Here's a code snippet for adding a new document in a collection:

const db = firebase.firestore();

db.collection("users").add({
    first: "Ada",
    last: "Lovelace",
    born: 1815
})
.then((docRef) => {
    console.log("Document written with ID: ", docRef.id);
})
.catch((error) => {
    console.error("Error adding document: ", error);
});

4. Summary

In this tutorial, we covered Firebase Authentication and Firestore Database. You learned how to authenticate users and perform CRUD operations on the Firestore Database. You can continue exploring Firebase features like Firebase Storage, Firebase Cloud Messaging, etc.

5. Practice Exercises

1. Implement a sign-up flow using Firebase Authentication and store user's information in Firestore.
2. Implement a feature that allows users to update their profile information stored in Firestore.
3. Implement a feature that allows users to delete their account and also delete all their data from Firestore.

Remember, practice makes perfect. Keep exploring and happy coding!