Following the release of iOS 11 into public beta earlier this week, Apple has followed up with the first public beta of macOS High Sierra. As an update focussed on refinement rather than lots of new features, it shouldn;t cause too much grief but a new file system and changes to how some some data is handled makes me think this one needs a "Handle with Care" label.
macOS High Sierra brings the Apple File System, that was introduced in a later release of iOS 10, to the Mac. It should make things like file moves and copies, and opening the Get Info panel a lot faster - almost instantaneous according to some.
If you're interested, Apple has a run down of the new features, as well as instructions of how to access the beta release.
If Apple follows the same pattern as past years, you can expect an update to the beta every two weeks with four or five betas followed by a couple of attempts at a release candidate before becoming officially released.
And all the usual caveats about beta software apply. Don;t use it on a production machine, be prepared for random flakiness and not all features are there or complete yet.