Magento 2 PWA allows you to create websites that are fast, mobile-friendly, and reliable.
There are some main components those makes PWA works with Magento 2.
1. Application shell
It provides the basic user interface structure for a progressive web application.
2. Service worker
It is a script that runs in the background. It is used for caching and resource retrieval in PWA.
3. Component data binding
It is a component of PWA which binds data flow between the source and a UI component. PWA use data binding patterns to connect dynamic data with the user interface.
It is used as a data query language at client side and a service layer on the server side in PWA. It request and push data in PWA.