Virtualization is a technique of sharing the single physical instance of an application, servers, storage device, operating system or resources among multiple customers or organizations. This technique assigns a logical name to physical storage and provides a pointer to that physical resource when demanded.

With the help of Virtualization, we can run multiple resources on the same hardware simultaneouslye time. Thus it increases the utilization of the hardware and makes it a cost-effective and energy-saving technique. 

The virtual machine on which the virtual machine is built is called the Host Machine, and the virtual machine is called Guest Machine.

Hypervisor: Hypervisor is software that creates and runs virtual machines; it is also known as a virtual machine monitor (VMM). The hypervisor allows the host machine to share a single physical instance of cloud resources among multiple organizations or clients. There are two types of hypervisors. 

1. Type 1 Hypervisor: The type 1 hypervisor doesn’t contain OS because they are executed on the bare system, which means it runs on the host machine's hardware. Examples of type 1 hypervisors are Oracle VM, VirtualLogic, Microsoft Hyper-V, VLX, Sun xVM, RTS Hypervisor, etc.
2. Type 2 Hypervisor: Type 2 Hypervisor is called hosted hypervisor because it runs inside an existing operating system of a physical host machine. Examples of type 2 hypervisors are Oracle VM Virtualbox, VMware workstation, Windows Virtual PC, VMware Fusion, Parallels Desktop, etc.

Types of Virtualization in Cloud Computing 

1. Operating System Virtualization: In operating system virtualization, the virtual machine software is installed on the host machine operation system instead of on the hard pe of Virtualization, which is used to test and run different applications on different operating systems.
2. Server Virtualization: In server virtualization, the software is directly installed on the server system. The server administrator divides one physical server into multiple servers per the demand basis and balances the load.
3. Hardware Virtualization: In hardware virtualization, the virtual machine software is installed in the hardware system. The hypervisor monitors and controls the memory, hardware resources, and process. Once the Virtualization is completed, the client can install multiple operating systems to run and test different applications.
4. Storage Virtualization: Storage virtualization is implemented with the help of software applications. The physical storage is combined to form multiple network storage devices that look like a single storage device. The storage virtualization is done for the backup and recovery process.