Not a stupid question at all, but a misunderstanding of what iCloud is and does.
iCloud is a syncing service, not an archive. All devices logged in to the same iCloud will have exactly the same contents, so of you add an item to any device it will appear on iCloud and on all other devices sharing the iCloud account. And likewise, if you delete an item from any device it will be deleted from iCloud and all other devices.
Here’s more detail: iCloud+ has 2 independent functions. iCloud backups, and iCloud sync. It’s confusing because they both have the same name prefix. But they have no connection with each other. Go to Settings/[your name]/iCloud. You will see a bunch of switches (with iOS 16 or later also tap Show All). When you turn on a switch that data type will sync to iCloud. If you do this on multiple devices that share an Apple ID the selected data will sync to all of those devices.
You can also turn on iCloud Backups. This will back up your phone every night if the phone is plugged in, connected to Wi-Fi and locked.
But note that anything that you sync by the first method will be excluded from the iCloud backups.