https://www.theverge.com/2017/9/25/16360890/apple-macos-high-sierra-mac-update-now-available

The latest big update to Apple’s desktop operating system, macOS High Sierra, has just been released as a free upgrade for users. It’s available now in the Mac App Store. All Macs from 2010 and later are compatible with the update, and some MacBooks and iMacs released as far back as 2009 can also run it. For a thorough look at all the new features that make up High Sierra, definitely read The Verge review.

After installing this update, you won’t notice many significant outward changes or redesigns, but the Mac’s core software foundation is in fact changing rather drastically. MacOS High Sierra includes a new, modernized file system — Apple File System (APFS) — and support for more efficient photo (HEIF) and video (HEVC) standards. HEVC, also known as H.265, is designed to efficiently handle 4K video without eating up too much storage on your Mac.