How does it actually free up space on my Mac and other IOS devices, to backup to iCloud.
I know it sounds obvious to most of you, but I dont really get what happens to original photos and videos on my Mac's harddrive, when I upload them to iCloud Photos. Because obviously it will affect my iCloud Photos, if I erased the original photos/videos on my Mac to free up space. What happens to it?
And additionally:
If I afterwards wanted to make an external hard drive or alternative cloud service backup, would that be backups redirected from iCloud Photos through my Mac to that harddrive or service?
MacBook Pro 15", macOS 10.13