The ServiceWorker interface of the ServiceWorker API provides a reference to a service worker. Multiple browsing contexts (e.g. pages, workers, etc.) can be associated with the same service worker, each through a unique ServiceWorker object.
The ServiceWorkerGlobalScope interface of the ServiceWorker API represents the global execution context of a service worker.
The ServiceWorkerRegistion interface of the ServiceWorker API represents the service worker registration. You register a service worker to control one or more pages that share the same origin.