Well that's a stupid question, isn't it? It's "Development done right", "Fast, Elastic, Dependable" and on "Any Cloud", right? If you are unclear as to what phpcloud.com is, what the Zend Application Fabric is and what the DevCloud is then this is a good post for you.
The phpcloud platform offers their own Zend Application fabric to provide resources based on the needs at the time and the DevCloud, a "slice" of these resources for you to try out for your development.
So, the Fabric is the loom, DevCloud is a thread spool and phpcloud.com is the lever you pull to start.