In 2016, the web browser became increasingly capable with powerful APIs like WebRTC, enabling it to connect voice calls with other browsers, mobile apps, and phones globally. The tutorial series explores how to use Twilio Client to establish a browser-to-browser voice call, using languages such as C#, Java, Node.js, PHP, Python, or Ruby. The tutorial is designed for developers working in various popular frameworks and languages, including ASP.NET MVC, Spark, Express, Laravel, Django, and Ruby on Rails. The goal of the tutorial series is to provide a comprehensive guide to implementing browser phone calls, with over 100 use case tutorials available at Twilio's documentation website.