From Mac Guides
iCloud, a SAAS (Software as a Service), is a collection of internet based services and software offered by Apple. It is a successor to MobileMe, Apple's previous SAAS.
iCloud comes with seven web applications available at http://www.icloud.com. The applications appear in a web browser as flush full fledged applications. The seven applications are:
- Find My iPhone
- iWork (still in development)
Almost all features and preferences available on the equivalent desktop software are also available through the web applications, integrating seamlessly with the synchronized software on the computer. Users can create or delete aliases, create/delete/modify contacts, and add and transfer calendar events and to dos. Web apps also fully support keyboard shortcuts for performing various actions across different applications.
iCloud includes an @icloud.com email address. When a message is received it is sent directly to all the user's devices. Supported devices include the Apple iPhone, iPod Touch, iPad, Apple Mail on Mac OS X, and Microsoft Outlook on Microsoft Windows. Users can also setup email aliases that will be redirected to their iCloud Mail account. Up to 5 aliases can be created. A single POP mail server may be configured to receive mails from. Mail forwarding is also supported. Spam filtering is absent.
Previous .Mac/MobileMe subscribers keep their @mac.com and @me.com email addresses and gain a new @icloud.com address. New iCloud subscribers (subscribed after transition) do not receive the @me.com or @mac.com address. The mac.com, me.com, and @icloud.com mail servers are interlinked meaning all have only one inbox.
Contacts and Calendars
iCloud maintains a synchronized address book and calendar feature. If a user makes a change to a contact or event on one device it will be automatically synced to the iCloud servers and, by extension, all the user's other devices. Supported devices include the Apple iPhone (and other members of the iOS family), Address Book and iCal on Mac OS X, and Microsoft Outlook on Microsoft Windows.
iCloud has only one plan, which is free. However, this one plan can be upgraded with additional storage for a monthly fee.