What you can do with iCloud storage
When you set up iCloud, you get 5 GB of free storage. You get more storage when you upgrade to iCloud+. You can choose an iCloud+ plan with 50 GB, 200 GB, 2 TB, 6 TB, or 12 TB of storage. For more information, see Upgrade to iCloud+ and manage your subscription and the Apple Support article iCloud+ plans and pricing.
About security and iCloud storage
You can protect your account with two-factor authentication, and many iCloud features require it. When you use two-factor authentication, you need to enter both your Apple ID password and a six-digit verification code to access your data. As extra protection for your Apple ID against phishing attacks, you can also use a physical security key instead of a verification code. See the Apple Support articles Two-factor authentication for Apple ID and About security keys for Apple ID.
All information stored in iCloud is encrypted, and certain iCloud features use end-to-end encryption. This means that only you can access your information, and only on devices where you’re signed in to iCloud.
For the highest level of cloud data security, you can turn on Advanced Data Protection for iCloud. With Advanced Data Protection for iCloud, your data can be decrypted only on your trusted devices, protecting you even in the case of a data breach in the cloud. Because Apple will not have the encryption keys required to recover your data, you need to have a Recovery Contact or Recovery Key set up on your account. You can use these additional recovery methods to regain access to your data if you ever forget your password or lose access to your account. See the Apple Support article iCloud data security overview.
Ways you can use iCloud storage
Here are some examples of what you can store in iCloud.
Photos and videos: You can use iCloud Photos to store your photo library in iCloud and see it everywhere. Your original, full-resolution photos and videos are stored in the cloud. Smaller versions of your photos and videos appear on your devices, but you can download the original versions at any time. See Share photos and videos and keep them up to date with iCloud.
Files: You can store your documents, presentations, and other files in iCloud Drive, and access them on all your devices and on the web. Your files stay up to date everywhere. See Keep your files up to date and share them with iCloud Drive.
iPhone, iPad, and iPod touch backups: You can use iCloud Backup to automatically back up your iPhone, iPad, or iPod touch to iCloud. Your backups are available if you ever need to restore a device or set up a new one. See What is iCloud Backup?
Learn how all your favorite apps use iCloud. See Apps and features that use iCloud.