Technologists tend to provide an overly-complicated answer to the question “what is the cloud?”. In the context of cloud hosting there is no physical object which you can point to and label as the cloud. It’s more of an electronic structure where data is stored over many different computers and served up via a network connection, typically the Internet.
When you get into cloud hosting these server farms behave as one large storage space and processor. The actual website data(such as HTML/CSS files, images, etc.) is spread out over a cluster of hard drives connected together, much like one virtual disk with tremendous capacity.
Server clusters can provide a cloud setup with literally unlimited machines to run through. You could also build a cloud space with just 5-10, so the methodology is scalable to boot.