If you have iCloud Photos turned on then your photos are synced with iCloud and with any other of your devices where iCloud Photos are turned on. Photos are not included in an iCloud Backup if you have iCloud Photos turned on; they are only included in an iCloud Backup if you do not have iCloud Photos turned on.
Regarding the Mac:
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: https://support.apple.com/mac-backup
And more information on syncing in:
Set up and use iCloud Photos - Apple Support
and
Access and manage files in your iCloud Drive - Apple Support