How to understand service worker registration's task queue?

A service worker registration has one or more task queues that back up the tasks from its active worker’s event loop’s corresponding task queues. (The target task sources for this back up operation are the handle fetch task source and the handle functional event task source.) The user agent dumps the active worker’s tasks to the service worker registration's task queues when the active worker is terminated and re-queues those tasks to the active worker’s event loop’s corresponding task queues when the active worker spins off. Unlike the task queues owned by event loops, the service worker registration's task queues are not processed by any event loops in and of itself.

How to understand it, why ua must dump active worker's task to service worker registration and re-queue it when it's active, what's the meaning of this？