Progressive Web App
In plain terms
A web app that behaves like a native app, including offline use.
Going deeper
PWAs use service workers and manifests to be installable, work offline, and send push notifications, blurring the line with native apps. They run in the browser yet feel native.
Under the hood
Service workers cache assets for offline; manifests enable home-screen install, with capabilities still trailing native on some platforms.
Examples
Twitter Lite, Starbucks PWA, offline-capable web apps, installable sites.
Think of it like...
Like a website that can move into your phone and keep working without internet.