What is iCloud storage?
When you sign up for iCloud, you automatically get 5 GB of free storage. Your iCloud storage can be used for iOS or iPadOS device backups, documents in iCloud Drive, iCloud Photos, app data and documents stored in iCloud, and iCloud Mail (your @icloud.com email account).
You can upgrade or downgrade your iCloud storage at any time. If you run out of space, you can remove stored items to make more space available. See the Apple Support article Manage your iCloud storage.
If you upgrade your storage to 200 GB or more and you’re the organizer of a Family Sharing group, you can share your iCloud storage with other family members.