How are VMware ESXi and ESX different than VMware vSphere?
VMware ESX and ESXi are two alternative architectures that customers can choose when deploying any of the paid editions of VMware vSphere(Essentials, Essentials Plus, Standard, Advanced, Enterprise, Enterprise Plus). On the other hand, the free edition of VMware vSphere, VMware vSphere Hypervisor, is only available in the ESXi architecture. All the functionality of VMware vSphere is supported by both the ESXi and ESX architectures. VMware vSphere clusters and resource pools don’t necessarily have to be based on hosts using the same vSphere hypervisor architecture. Customers can choose to cluster vSphere hosts that use ESXi architecture with vSphere hosts that use ESX.