iCloud vs iCloud backup

What it does, depends on what option exactly you have turned on or not.

If you have iCloud Photos turned on in Settings ➜ Photos, then it syncs photos to iCloud and anything you remove locally on a device or computer will sync and be removed from iCloud as well.

If you don't have iCloud Photos turned on, then the iOS device backup process can actually backup the photos in the photos app to iCloud if the option is turned on in Settings ➜ Account (top of Settings) ➜ iCloud ➜ iCloud Backup ➜ Your iPad ➜ Photo Library. This backup is not directly accessible by you, and can only be restored to a device during setup. Deleting items from your device will not affect the backup until the next time the backup is updated.

To backup to an external drive from an iPad or iPhone, you would need to do so manually, by connecting the external drive to the iPad, and then in the Photos app, selecting the photos to be copied over, then tapping on the share icon at the bottom of the screen, then tap on Save to Files, and then navigate to the connected external drive to save them onto it.

click here ➜ Connect external storage devices to iPad - Apple Support

In either case your photos are backed up

This is incorrect. iCloud Photo Library is not a backup, and should never be considered as such. iCloud Photo Library is a synchronization service. The photos are not backed up. Anything deleted from your device will also be deleted from iCloud automatically and there is no way to get it back as there is no actual backup of them anywhere.

jefffrominvers Said:

"iCloud vs iCloud backup: [...]What is the best method to backup to an external hard drive?"

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Creating an iCloud Backup:

Use My User Tip: Getting a Quick and Direct "iCloud Drive-to-External Hard Drive" Download - User Tip

I can't answer your question about the accuracy of what you read, but my iCloud account is performing both backup support and permits my devices to sync with each other. To turn on backup support for iPhone or iPad, go into System Settings>Apple ID>iCloud>iCloud Backup. More, you'll need enough storage space to support your device's backup, and you must set this up on each device. Finally, it appears that the iMac does not have iCloud Backup support in system settings.

Link to iCloud Backup here: How to back up your iPhone or iPad with iCloud - Apple Support

Speaking specifically about iCloud backup for photos: If you use iCloud Photos, then your photos are saved in iCloud, but not in the iCloud backup file. If you are not using iCloud Photos, then your photos are backed up in the iCloud Backup file.

In either case your photos are backed up. The same is true for data stored on your phone. You have the choice to use iCloud to save the data or have the data saved on your phone, which will be included in your backup file.

In your iCloud settings, you can choose which apps will save the data in iCloud. You do need to make sure iCloud Backup is turned on to have your phone save a backup to iCloud.

To summarize iCloud is both a syncing action, by making the data/photos available to all of your devices, and a backup option when turned on to provide a backup of your individual device.

I was referring to the instance of if you restored your phone, you will get your photos back. It is a backup in the sense they are the exact photos that you had on your phone and that is what is saved in the iCloud Backup option in settings, but it is true that if you delete them from your phone, the backup file will not include them.

The Op's question was "iCloud vs iCloud Backup" and in both of those cases your photos are saved in iCloud with the difference of the iCloud Backup option without iCloud Photos saves the photos that you have on your device in the Backup file that you restore, and the iCloud Photos saves them independently from the Backup file.

Mac Jim ID wrote:

I was referring to the instance of if you restored your phone, you will get your photos back. It is a backup in the sense they are the exact photos that you had on your phone and that is what is saved in the iCloud Backup option in settings, but it is true that if you delete them from your phone, the backup file will not include them.

The Op's question was "iCloud vs iCloud Backup" and in both of those cases your photos are saved in iCloud with the difference of the iCloud Backup option without iCloud Photos saves the photos that you have on your device in the Backup file that you restore, and the iCloud Photos saves them independently from the Backup file.

The distinction is extremely important though because, synced photos, if deleted from the iOS device are also deleted from iCloud. I can't count the number of people who have posted here saying, "I backed up my photos to iCloud, deleted them on my phone and now they're gone!?!" Of course, what they'd really done was synced to iCloud. So, while your explanation is not exactly incorrect, I think it could lead to that very situation.