Does the ICLOUD back up my Mac

No, it does not.

TimeMachine is still the built-in means to backup Macs. (Plus there are numerous 3rd party solutions)

iCloud backups are modeled around backing-up and easily restoring easily-lost iOS devices.

However … Data folders on a Mac CAN be on iCloud and kept sync’d.

This has the advantage of distributing copies of your data which is better than nothing …

… BUT if you inadvertently delete from any one place, it STILL “syncs” … deleting it everywhere. You can’t “roll it back” to 5 days ago like you can a “real” backup.

If you are using iCloud to store documents and desktop in iCloud and other documents on iCloud Drive, iCloud will just store the current state of your documents and data. If you Mac should get lost or damaged stolen, you will get the current state back from iCloud. You need backup scheme to save a history. and if you are using "Optimize Mac Storage with iCloud, to save local storage, ir will be much more work to make regular backups.

You should be aware, that many of the backup methods for a Mac may no longer work and can no longer make complete backups, when your documents and data are in iCloud, but not on your Mac as well - Time Machine or Cloning software can only backup the items, that are stored locally on your Mac. If you are using iCloud and optimize Mac Storage you have to download regularly copies of your cloud data, or you no longer have a complete backup of your data, even with Time machine backing up your Mac continually. Archive or make copies of the information you store in iCloud - Apple Support