Virtualization is the primary technology that powers cloud computing. It is the technique that enables one to share an application or physical instance of a resource among organizations and multiple other users. It separates the computing environments from the physical infrastructures. It enables users to simultaneously run various applications and operating systems on the same machine. Server consolidation is the biggest advantage of virtualization. It allows splitting the resources of a single server for multiple utilities. The machine that serves as the virtual device is the host machine. The virtual appliance is called the guest machine.