What is iCloud?

What is iCloud?
iCloud stores your music, photos, apps, calendars, documents, and more. And wirelessly pushes them to all your devices — automatically. It’s the easiest way to manage your content. Because now you don’t have to.

http://www.apple.com/icloud/what-is.html

iCloud includes:

  • iTunes in the Cloud
  • Photo Stream
  • Apps, Books, Documents and Backups
  • Contacts, Calendar and Mail
    (this is the MobileMe component)