The macOS High Sierra 10.13 operating system, as you most likely know, was recently released bringing many new features and improvements, starting with the new APFS which is superior to HFS+.
APFS (Apple File System) is a brand new advanced storage architecture created by Apple to provide a foundation for future storage technologies on the Mac. It comes with even more features than the HFS+ file system used in previous versions of macOS, including macOS Sierra 10.12.
Specifically, APFS supports all the latest high-capacity storage devices, is more reliable and secure, and provides improved performance. It is also much faster than HFS+, making operations like copying or moving large files and folders with many items almost instantaneous.
APFS can also protect your data from unexpected disasters such as system crashes or power outages. It is available with the latest macOS High Sierra 10.13 for all supported Mac computers with internal flash storage.
Unfortunately, APFS is not supported on Mac systems with hard disk drives (HDDs), nor on Fusion drives, which are found in some iMacs and Mac minis. Apple has said it will add support for these drives in a future update to macOS High Sierra, which was recently confirmed by Craig Federighi.
We would like to emphasize that it would be a good idea to not update your Mac with MacOS High Sierra for now as a critical security issue has been identified that puts your passwords stored in Keychain at risk.
