Cloud computing is when you have a virtual (server, VPS, or shared space) that is split up on multiple physical servers.
You still have the same "power" (ram, CPU, etc) as a regular VPS. The benefit is some added redundancy that will keep your server online if one physical server goes down.
Cloud VPS is a good thing, but often not worth the expense. A quality host will have systems in place to ensure their servers stay online.
The most common cause of site downtimes is poor programing, hacking, DDoS, etc, and Cloud VPS won't help with that.