Progressive Web Apps are web apps that use emerging web browser APIs and features along with traditional progressive enhancement strategy to bring a native app-like user experience to cross-platform web applications. Progressive Web Apps are a useful design pattern, though they aren't a formalized standard. PWA can be thought of as similar to AJAX or other similar patterns that encompass a set of application attributes, including use of specific web technologies and techniques. This set of docs tells you all you need to know about them.