iCloud & iCloud Photos · iCloud Drive basics
Is iCloud Drive a backup of my Mac?
Short answer: No. iCloud Drive syncs the same copy across your devices, so a deletion or overwrite spreads everywhere. Keep a separate backup too — Time Machine or Storage Studio's Data Backup, which keeps versions you can restore.
No. iCloud Drive syncs files — it keeps the same copy on all your devices. If you delete or overwrite a file on one device, that change syncs everywhere, so it isn't a separate copy you can go back to the way a backup is.
iCloud.com does keep recently deleted files for a while, which helps with accidents, but it isn't a versioned history of your whole Mac.
For real protection keep a backup as well — for example Time Machine to an external drive, or Storage Studio's Data Backup, which keeps versions of the folders you choose on another drive or a cloud account you've connected. See backups.