A PWA is both a website and an app at the same time - basically, a hybrid of the two.
Like a website, a PWA works on every device and browser, is linkable through a URL, and is visible to search engines.
Like an app, it installs to a user’s phone, can work offline, has a home screen icon for easy reengagement, is secure, and offers full screen navigation.
In other words, a PWA is a website that is generally faster, more reliable, more secure than a traditional website, and that can also look and behave like an app. It’s also an app that works everywhere and can be shared with a link.
From a technical perspective, PWAs have “manifests” and “service workers” that regular websites do not have. The “manifest” is where the app short name, icon, splash screen color, and other metadata for app characteristics are stored. Service workers allow PWAs to run background processes in the user’s browser. An example would be collecting engagement metrics so that one does not have to rely on google analytics or tracking cookies to measure views and interactions.