I have been reading about openstack and got very interested in it. my purpose is to try it in my office to get accustomed to it. the first purpose is to provide VMs for developes to do their server environment test on it on their own (policy). The ultimate purpose would be providing a sort of SAAS for people where each VM is deployed with a domain name, an OS with our application running on tomcat. the implementation is still blurred so I need to try out couple of things to acquire the right perspective(s). I know that I should consider openstack for bigger deployment like starting from 50+ nodes so I think it's best to have a close look at openstack. Pardon my ignorance and allow me to pickup ideas, experiences , knowledge and best practice from all of you.

Is is safe to say VirtualBox for example is an hypervisor? If that is the case does openstack not providing the same kind of functionality where on a physical machine (or cluster of machines) one can create different OSes as per Virtual Machine?

When providing explanation kindly try to avoid too much technical terms for now.

Thank you