A cloud web hosting service means that each part of your world-wide web presence will be handled by a separate server. For instance, your files and databases will be handled by different machines and since just one single type of processes will run on a server, each machine will perform better and will use its resources to the fullest. Whether you'll get a real cloud service or not also depends on the control panel that you will use to control your account. Since most control panels were intended to operate on a single server, they are unable to work on a cloud platform whatever a given web hosting service provider could advertise. In case one service stops responding, the whole server could go down, so your websites won't be accessible. This is the reason why you should check what service you will actually receive if you are looking for cloud hosting before you buy anything.