Apple offers iCloud Backup for iPhones and iPads but not for Mac computers.
If you are syncing files with iCloud, if you move the folders to the iCloud Drive folder they will sync. Also, if you have the Desktop and Documents option of iCloud Drive turned on, then files in those folders will also sync.
You can access the iCloud Drive folder via the Finder sidebar or the Finder "Go" menu.
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 the Apple article: 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