Almost everyone who uses the internet uses the cloud, wittingly or no, but it seems that few people actually know what it is.
In much the same that when we think of farming we think of rolling green pastures and cute red barns while the reality is that most farming is an industrial endeavor involving big metal buildings and huge machinery when we think of the cloud, we think of, well, a cloud. I still catch myself doing that and I love watching video tours of Google's huge data centers.
Metaphors aside, when we store files in the cloud they are really being stored on physical hard drives, though probably much bigger, nicer ones than the one in your computer. These hard drives live in vast warehouses that are constantly fighting tooth and nail to keep the temperature low enough for everything to run well. The hard drives and computers in there get warm the way your computer gets warm, but there are thousands and thousands of them.
But enough of my weird obsession with data centers. If this infographic hasn't convinced you the cloud is on your side, I don't know what will. We've got more cloud computing info for you in this cloud computing for enterprise infographic.