Does MacOS Support a Snapshot-Style Filesystem?
Apple's new file system, APFS, supports snapshots.  Per their documentation:



APFS is available in 10.12.x (Sierra) as a Developer Preview and as a released product in 10.13.x (High Sierra).

Earlier than Sierra, if you need to make a "point in time" backup, it's best to run Time Machine to ensure a good backup.