You can store documents, keep files and folders up-to-date across all your devices, work on items and access them from anywhere using iCloud Drive. Changes applied to a copy of a file on one device will automatically sync across all your other systems.
iCloud Drive is a real file system, so you can create and save items to your own self-created folders, which useful if you work across multiple devices. (You must use a Mac to create your own folders).
If you use iCloud Drive across multiple Macs then changes made to the Documents and Desktop files on both Macs will sync. The Mac you activate last will create its own folder for the contents of its Documents and Desktop, and this will also sync.