When you sign up for iCloud, you automatically get 5 GB of free storage. Your iCloud storage is used for iCloud Backup, app data and documents stored in iCloud, and iCloud Mail (your @icloud.com email account). If you need more storage space, you can upgrade to a larger storage plan. For more information, see the Apple Support article Storage upgrade pricing.
Note: You can change your iCloud storage plan at any time. Your storage upgrade is billed every year unless you cancel by downgrading your storage plan from your iOS device, Mac, or Windows computer. When you request a downgrade, it takes effect one year after your storage upgrade was initially purchased.