Apple Inc. (AAPL) Chief Executive Officer Steve Jobs on Monday officially unveiled the iCloud -- which stores music and other files online and keep devices synchronized wirelessly -- at the 2011 Worldwide Developer Conference (WWDC).

Today it is a real hassle and very frustrating to keep all your information and content up-to-date across all your devices. iCloud keeps your important information and content up to date across all your devices, Jobs said in a statement. All of this happens automatically and wirelessly, and because it's integrated into our apps you don't even need to think about it-it all just works.

The free iCloud services include, among others, the former MobileMe services, App Store and iBookstore, iTunes and Photo Stream service. iCloud includes 5GB of free cloud storage for Mail, Document Storage and Backup.

The content stored in the iCloud can be accessed across different Apple devices, including the iPhone, iPad, iPod touch, and Mac, or even a PC. Any updates, saves and changes will be made automatically across all registered devices.

Previously, Amazon and Google launched the Web-based music service Cloud Player and Google Music Beta. But with iTunes' dominance in digital music, Apple's iCloud could dominate the market as its offering differs from both players in big ways.

How iCloud Differs from Other Google and Amazon Services

* iCloud lacks one major feature compared to other players: online streaming. Apple has confirmed that it does not have Web access like Amazon Cloud Drive and Google Music Beta. The music must be fully downloaded to play.

* Apple’s iCloud was not solely created for music; rather, it has functions that allow it to hold e-mail, a phonebook of contacts, a calendar, iOS device photos, app data and iWork documents.

*The strong point in favor of Apple is how you get music up to the cloud. With Google and Amazon's services, you have to wait for the actual data to upload from your computer or device. This can take time, if you are dealing with a big music collection. Apple iCloud defies these lengthy upload hours as it has high-resolution versions of 18 million tunes available and stored in its servers. These are used as copies for your immediate streaming or uploading in the future.

Rumors suggest that Apple got into agreements with Universal Music Group, EMI Group, Sony Music Entertainment and Warner Music Group in order to come up with all these online copies. Consequently, Apple charges $24.99 annually for non-iTunes purchased music to be stored online.

*Cloud Drive offers 5GB storage for free and provides an extra $20/year for 20GB and $1000 a year for 1TB. Songs bought on Amazon don't count against the limit, while Google's Music service is free this year if you can procure an invitation to join. Apple's iCloud provides 5GB of free cloud storage for Mail, Document Storage and Backup. Purchased music, apps, books and Photo Stream do not count against the storage limit. ICloud will only store photos for 30 days.