Serenity Caldwell writing at iMore:
Do not upload all your tracks from iTunes to iCloud, then delete the local copy on your Mac. If you do that, you're getting rid of your original, DRM-free copies. And you're leaving yourself without a physical backup of your data, which I never, ever recommend.
"The cloud" doesn't equal backup. This statement is found within a thurough article clarifying Apple Music and tracks which might be stamped with Apple's digital rights management (DRM). For those especially in love with Apple Music, such as myself, it's a helpful read.