Put simply, a Progressive Web App (PWA) is a web app that uses modern web capabilities to deliver an app-like experience to users. These apps are deployed to traditional web servers, are accessible through URLs, and can be indexed by search engines.
A Progressive Web App is, for all practical purposes, just another term for a website that has been optimized for mobile performance and that utilizes newly available Web APIs to deliver features that are similar to a traditional native app, such as push notifications and offline storage.
Capacitor has first-class support for Progressive Web Apps and native apps. That means that Capacitor's plugin bridge supports running in either a native context or in the web, with many core plugins available in both contexts with the exact same API and calling conventions.
This means you'll use
@capacitor/core as a dependency for both your native app and your Progressive Web App, and Capacitor will seamlessly call web code when required and native code when available.
Additionally, Capacitor offers a number of utilities for querying the current platform to provide customized experiences when running natively or on the web.
For more details on how to convert this app to PWA, check the official documentation on Ionic framework website.