iCloud is a suite of free cloud-based services from Apple that helps users store and synchronize digital content across computers and numerous iOS-supported devices such as iPhones, iPads and iPod Touches. iCloud serves as the successor to Apple's MobileMe service and is included free as part of Apple's iOS 5, which first became available in October 2011. The service provides users with an initial 5-GB of iCloud storage for free, with additional storage capacity available for purchase on a monthly basis.
iCloud enables automatic synchronization across computers and iOS devices of e-mail mailboxes and messages, calendars, documents, photos, iTunes music and more. Apple also includes an iCloud Backup service that will automatically back up all iOS device data to the cloud, further facilitating synchronization across iOS devices without the need to connect to a PC or Mac via USB and use iTunes for synchronization.