However, some people don't want to enable iCloud service for some reasons like they don't feel comfortable to upload their personal data to a third-party service and worry that their data might be accessed by any unauthorized users. If you enable the iCloud service on your iOS device, Mac or Windows, you are able to sync data among your iDevices, access freely the contents on your device anytime and anywhere, and also restore data on iDevice from iCloud backup.
ICloud, as the Apple's cloud storage service, allows you to securely store your personal files like photos, videos, documents, music, apps and etc.
