If you browse to your webmin installation on a mobile phone browser you will get an option to install webmin as an app. Look in the menu.
This is not a real app but will run the webmin website in a containerised browser and will function like an app such as keeping you logged in and having its own icon in the phones app section, and so on.
Yeah, essentially it is a shortcut that behaves more like a native app. It leverages a technology called service workers. These are scripts that run in the background of the browser, enabling features such as offline functionality, background synchronisation, and push notifications.
PWAs rely exclusively on Safari’s WebKit engine, which can constrain their performance and capabilities compared to Android counterparts.
Apologies for the earlier mistake; it was late when I responded. The correct information is: “It has nothing to do with Webmin. Every website can be turned into a PWA shortcut by adding it to the home screen.”