I'm having trouble getting my head around iCloud Drive, and the difference between it and iCloud. I've read the Apple information and FAQs, but am still confused. If an iPhone or iPad is filled with photos can they be moved to iCloud drive, freeing up space on those devices? It seems like iCloud is mostly for syncing between devices, so if you delete something in iCloud it's deleted from your device too. But does iCloud Drive also sync? I'd like to find someone or something who can explain these two services in plain language.