Apple's about to introduce Service Workers in Safari 11.1. So. what are Service Workers, and why might they matter to you or your enterprise?
Web apps unleashed
First introduced in Safari Technology Preview 46. Service Workers allow background scripts to power offline web applications and should make it possible (for example) for developers to build Web apps that can work even when offline.
This may mean web services you can save to your Home screen like any other app, use of the camera from within a web page, background sync and other ways to make web apps that will work on, or off-line.