How are PWAs different than normal web apps?
How does a Progressive Web App differ from a normal web application? Fortunately, you're most likely already doing most of what's needed for a PWA, like responsive web design.
PWA do rely on a couple of new technologies on top of what you may be used to. These are:
Web App Manifest
The Web App Manifest is a JSON file that describes the application to the browser. It defines the application's name, colors, icons and how it should run if installed to a device. Creating one is as easy as creating a JSON file and linking it from your HTML file. The manifest file can be linked from several pages to indicate to the browser that they all make up one app.
ServiceWorker is event driven and can be woken up by the browser if needed, even when the user is not on the page. This allows you to send users push notifications for important events like when an item is shipped or when a user receives a message. Because it is event driven, it cannot run tasks by itself and consume resources on your device.