As expected following Apple's purchase of the iCloud domain from Sweden-based Xcerion earlier this year and the construction of a US$500 million iDataCenter in Maiden, North Carolina, the company has revealed details at WWDC of exactly what its iCloud service will offer. By storing user's content in the cloud so it can be automatically pushed to various devices, iCloud will let users sync apps, media, documents, calendars and more between their various mobile iOS devices and a Mac or PC wirelessly.

iCloud, which can be turned on after upgrading to iOS 5, will provide 5GB of free storage for mail, documents, photos and backup data including device settings and app data. Thankfully, music, apps and books purchased from Apple won't count towards the 5GB, nor will the storage required for the new Photo Stream service that automatically uploads photos taken or imported on any device and wirelessly pushes them to all devices and computers. Extra storage will be also available for purchase at prices to be announced when the service goes live.

Daily iCloud backup for iOS devices will occur automatically over Wi-Fi when they are being recharged so as not to drain the device's battery or the user's mobile data quota.

With a tap of the iCloud icon, apps and books purchased from Apple on one iDevice can now be downloaded on up to 10 other iOS devices at no extra cost. Additionally, changes to documents created on iCloud compatible apps, such as Apple's iWork suite, will automatically be pushed to all the user's other devices.

iCloud also includes services previously available through MobileMe, which iCloud replaces, including calendar sharing, contacts, and an improved ad-free push Mail account hosted at In a godsend to users annoyed with the inability to simply mark message as read on iOS devices that meant needlessly opening the same messages on multiple devices, inboxes and mailboxes will now be kept up-to-date across all iOS devices and computers.

Photo Stream will automatically upload photos taken or imported on any devices to iCloud where they will be stored for 30 days so they can be wirelessly pushed to all devices and computers. Photo Stream will be built into iOS device photo apps, iPhoto on Mac, and will save images to the Picture folder on PCs. While Macs and PCs will store all photos from the Photo Stream, only the last 1,000 photos will be stored on each mobile device to save storage space.

Finally, there's iTunes in the Cloud and iTunes Match, which we already took a look at here.

While iTunes in the Cloud is available now to U.S. residents, iCloud will go live this fall (northern hemisphere) with the release of iOS 5.