icloud backup protocols

Apple offers iCloud Backup for iPhones and iPads but not for Mac computers.

It is possible to sync data from a Mac to iCloud if you turn on those options (e.g., iCloud Photos, iCloud Drive including the Desktop & Documents option). Syncing has some of the benefits of a backup (and the benefit of being offsite) but is not the same as a backup. Major differences include the fact that not everything on your Mac can be synced and the fact that if you delete something, accidentally or otherwise, there is only a limited time period (30 days in most cases) during which it can be recovered.

Also see: How to back up your Mac - Official Apple Support

And more information on syncing in:

Set up and use iCloud Photos - Apple Support

and

Access and manage your files in iCloud Drive - Apple Support

and

Add your Desktop and Documents files to iCloud Drive - Apple Support

You can't use iCloud for complete Mac back up , simply turn on iCloud features from Mac system preferences that includes iCloud Drive , desktops and documents Use iCloud Drive to store documents on your Mac and iOS devices - Apple Support , the inbuilt applications like , notes , photos , mails .....that sync the iCloud data saved with applications to iCloud Set up iCloud on all your devices - Apple Support

Introduction to iCloud - Apple Support

Other ways to back up and restore files - Apple Support

Note : the correct way to save Mac back up is use time machine Back up your Mac with Time Machine - Apple Support