its a similar concept but with important differences. It checks to see what is already in the "cloud" and if the data you are uploading eg: songs already exists and if it does then you dont have to upload your version you simply have access to whats already there, saving on bandwidth.
Also the cloud becomes your hard drive which is infinate so you dont keep them locally any more at all, once you have "cloudified" a folder instead of saving it locally you save it to the cloud. They also have a web portal that allows you to access this from anywhere with an internet connection.
handy for logging in at your families house and showing photos/videos. etc
You are also able to "cloudify" external drives and once disconnected you can still access your data -esentially you could get rid of all externals this way.