iCloud helps you keep your most important information—like your photos, files, notes, iCloud Keychain, and more—safe, up to date, and available across all your devices. It’s built into every Apple device, and everyone gets 5 GB of storage to start. (Purchases you make from the App Store, Apple TV app, Apple Books, or iTunes Store don’t count toward your available space.)
So if you have an iPhone, iPad, or iPod touch, just sign in on each device with your iCloud.com, or on a Windows PC in the iCloud for Windows app. When you make changes to a file on a device or on iCloud Drive, you can see your edits wherever you view the file.
To get started, open Use iCloud Photos on iCloud.com in the iCloud User Guide.
Enjoy your purchases anywhere. When you’re signed in to your devices with the same Apple ID, purchases you’ve made on the App Store, Apple TV app, Book Store, and iTunes Store are available at any time, no matter which computer or device you used to purchase them. So all your music, movies, books, and more are available wherever you go.
Locate your iMac with Find My Mac. If your iMac is missing and you have Find My Mac turned on, you can use What is iCloud? in the macOS User Guide.