In order to be a Progressive Web Application, the Intershop PWA implements some advanced concepts matching those criteria.

Web App Manifest

The Web App Manifest enables the PWA to be installable on home screens of mobile devices.
The application is easily accessible via a generated link and branding is applied to icons and browser coloring so it poses as a native application.

The manifest in the PWA is theme specific and can be customized in the file src/assets/themes/<theme>/manifest.webmanifest.

Service Worker

Service Workers are automatically installed into client device browsers after the first visit to the shop and take over all the handling of the application on the client side.
Possible advanced features supplied are offline-capabilities and push notifications.
After installation, the service worker effectively disables server-side rendering for clients and invokes all rendering on the client himself.

For the Intershop PWA, offline browsing is not a suitable use-case for most customers and push notifications are not yet supplied by the Commerce Management Suite.
For now service worker integration is an experimental feature that can be activated for appropriate projects.

To activate the service worker run

node schematics/customization/service-worker true

To run the project as a Progressive Web App with an enabled Service Worker, use npm run start to build and serve the application.
After that open http://localhost:4200 in your browser and test it or run a PWA audit.
Currently only localhost or 127.0.0.1 will work with the service worker since it requires https communication on any other domain.

You can also activate the service worker specifically for docker builds by supplying the build argument serviceWorker=true.