macOS 10.13, aka macOS High Sierra
Apple announced macOS High Sierra at WWDC 2017 in June. This is macOS 10.13 and it is a free update for Apple computers that run macOS Sierra.
Here's a look at the new macOS High Sierra features that include upgrades to the Photos app, Safari upgrades to speed and control of autoplay sound, Siri features, VR support, external GPU support, Messages in iCloud and much more.
You can test out the update as part of the macOS High Sierra beta or you can wait for a full release later this fall. We expect to see Apple announce some new features during a special event in September.