Pick up right where you left off on another device
A document you were working on on your iPhone can be opened and continued on your iPad or Mac without manually transferring anything, since it already lives in the same iCloud Drive folder.
Keep storage use in check
iCloud Drive shares its storage allotment with photos, backups, and mail, so a free account fills up faster than you might expect -- checking usage under Settings > [your name] > iCloud regularly helps you avoid a sync interruption.
Frequently Asked Questions
Can I access iCloud Drive on an Android phone?
There is no native Files app integration, but you can view and download files through a web browser by signing in at iCloud.com.
What happens to a file if I turn off iCloud Drive?
You will be asked whether to keep a local copy of your files on that device or remove them, so make sure to choose to keep a copy if you still need access to them.