Apple's newly-unveiled iCloud service is one of several emerging cloud computing offerings, that are reducing the need for a conventional computer. But what does it actually mean?

The popular buzzword of "cloud" simply means storing data on someone else's computer servers, and accessing it by internet. And chances are, many people are already using it, by way of Google's Gmail service, social networking sites like Facebook or photo-sharing site Flickr, all of which store digital information on data centers all over the world.

But many are concerned about the potential downsides of cloud computing. In exchange for convenience, the technology could make personal data less secure.