A hybrid cloud offers the promise of uniting resources across multiple cloud providers, including those running different virtualization technology stacks. Creating a resource pool that cuts across silos increases efficiency and flexibility relative to constraining a workload to some subset of the overall capacity.
Furthermore, a hybrid cloud adds a layer of abstraction to the underlying technology platforms. Doing so can simplify management operations by masking the operational differences between different clouds or virtualization technologies.
A cloud needs to embody several characteristics in order to fulfill the above promise.