Welcome to Chapter 12! This is definitely my favorite chapter, as we will be building many end-to-end use cases for our application.

A gentle warning—this chapter is dense—it is packed with a ton of information. You may have to read it at a slower pace and spend more time at the keyboard than you have with the previous chapters, but, I must say, it is well worth the effort. 

Here is a great way to look at the overall progression of this book:

• Everything we've looked at so far, including the two most recent chapters (Chapter 10, Working with Forms, and Chapter 11, Dependency Injection and Services), has laid the foundation for this chapter. With that knowledge under our belts, we are now ready to put it all together in order to create our application. So, in essence, this chapter also serves the purpose of reviewing many of the topics we covered in previous chapters.
• This chapter is the pivotal turning point for us because we will take everything we've learned thus far to build 95% of our application in this single chapter. This is a lot of material for one chapter, but we have spent a good amount of time going over all the aspects of Angular that we will need to build our application, so we're going to breeze through it. There is some new and slightly off-topic material too—learning how to build backend APIs—which is less important than the Angular material. However, we need to have an API, so I selected a set of technologies that are simple enough to quickly get up to speed with. We are also going over this to help you get your mind around the technologies we will be using to construct the APIs.
• In the chapters that follow this one, we will add a couple of things to our app (such as route guards and custom form validation) and we will learn how to test, debug, secure, and deploy our application.

So, from that perspective, we're good to go. Many sections in this chapter are bonus material that I deem important to learn about because I want you to succeed, not only as an Angular developer, but as a web developer in general. This will help you to enhance your skills, and hands-on examples are sure to augment your technical knowledge as a web developer. 

We will cover the following topics:

• ListingApp – an overview
• Fundamental concepts for Angular applications
• ListingApp – technical requirements
• Building APIs for our application
• The Google Firestore database
• Angular HttpClient
• Integrating backend services

We've spent a lot of time in this book discussing a myriad of things—mostly Angular-centric (such as components, routing, flex-layout, NG Bootstrap, Angular Material, and working with forms), and a few things that were standalone (such as wire-framing, ES6, TypeScript, and Bootstrap). It is important to possess all that knowledge, of course, but we haven't yet integrated live data to bring our Angular application to life. However, as you can see from the previous bullet-point list, this is about to change. This is where developing in Angular starts to get fun, and also much more practical, since an application that does not create and consume data is not much of an application at all. 

OK. Let's get right into it by starting with learning about some of the fundamental concepts that form the foundation of any application. Then, we'll take a look at the steps involved in building our ListingApp.