APFS Explained: What You Need to Know Apple’s New File System

Apple’s macOS 10.13 High Sierra brings a new file system named “Apple File System”, which largely replaces the older HFS+ file system. Apple File System, also known as APFS, has been used by default on iPhones and iPads since iOS 10.3, and is also used on the Apple Watch and Apple TV—but now it’s finally on the Mac, too.
by Chris Hoffman via How-To Geek