Red Hat OpenStack Platform is a commercially supported distribution of open source OpenStack software designed to build and manage large pools of compute, storage and networking resources in public and private clouds.
Red Hat Virtualization is a hypervisor + hypervisor mangement project based on the opensource KVM hypervisor and the opensource oVirt hypervisor mangement project.
What this all boils down to is a comparison of OpenStack and oVirt. On the surface, they seem quite similar: virtualization management. But their focus is quite different. OpenStack targets massive scale and disposable virtual machine workloads. (Similar to public cloud.) oVirt focuses on smaller scale environments where the virtual machines are specialized and not disposable. (Similar to VMware.)
And to address the second half of your question, how they can work together: RHV can use individual components of OpenStack to provide various functionality (like networking, storage, etc.). OpenStack can use the hypervisor portion of RHV as a hypervisor under its compute service. Additionally, we can connect RHV to OpenStack using the OpenStack Neutron networking project.
Hope my answer will help you,Thanks.