I'm beginner on ServiceWorker. Today I saw this website : https://developers.google.com/web/tools/workbox
But I still have no idea what it is. Is this a library that help me make SW with easier way? Or, Is this another way to make PWA without SW?
What could be precise definition of "Workbox"?
It is a library for working with Service Workers. But not only Service Workers, but also other things considering Progressive Web Apps such as manifest.json files.
The page you linked says:
Why Workbox?
Workbox is a library that bakes in a set of best practices and removes the boilerplate every developer writes when working with service workers.
Precaching
Runtime caching
Strategies
Request routing
Background sync
Helpful debugging
Greater flexibility and feature set than sw-precache and sw-toolbox
which is a good definition.
Workbox will either: