Chris Ferdinandi has been writing an excellent post series on Service Workers. After first explaining what Service Workers are and how to create one, he — as per usual on Go Make Things — also provides us with practical scenarios such as making pages available offline, caching web fonts to improve rendering, etc.
Go Make Things: Service Workers →
☝️ You should really follow Chris’s blog as his Daily Developer Tips — in which this Service Workers series appeared — are always very good.