When it comes to web hosting, cloud architecture refers to using an individual server for each and every part of the hosting service. Such a setup results in improved performance since one machine will be used only for file storage, a different one only for running databases, etcetera, thus different system processes will not run on the exact same machine. This will decrease the chance of system errors considerably and will allow your sites to operate faster, not mentioning the higher uptime. In case you are looking for such a service, you should double check that you will really get it because lots of companies advertise cloud internet hosting plans, but the control panels they use are not designed to function in a true cloud and can work only on one server. The trouble with using one machine is that in case one service fails or generates high load, the whole server will possibly go offline, so your websites will no longer be accessible.