Apple’s iCloud is for iPhone, iPad and Mac cloud data syncing platforms activated by default for every Apple ID on any Apple device. Apple iCloud was introduced by Apple after the failure of MobileMe cloud offerings for Apple iPhone, iPad and Mac.
In day-to-day life, it may happen that you may accidentally delete or lose your Apple Address Book contacts or Safari Bookmarks or Calender data. But there is a way to restore in the case of loss. You can go to iCloud.com to restore your missing data from an earlier version.
Once you restore old data with current data, the existing data will get replaced. The restoration process can be undone in case of any glitches.