In this chapter, we learned what the REST API is, including details on authentication and the different kinds of API requests you can make. We also saw how to get started with the PHP library (as well as how to find the libraries for other languages).

Alongside the API libraries, we interacted directly with the API using Postman, which is a great Chrome app, to get more down and dirty with the barebones of the API.

We mastered the Calls and Messages API and saw how we can use the various Phone Number APIs as well as the Subaccounts and Usage APIs to make our applications even more powerful.

In the next chapter, we'll look at the innovative Twilio Client tool, which enables you to make calls within your browser (or mobile app), removing physical phone hardware from the equation.