Virtualization can be implemented in 2 ways:
1) Hardware Virtualization/ Type 1 Virtualization/ Bare Metal Virtualization:
Vmware vsphere Comes here
Here, the virtualization software directly runs on the hardware. It does not need any Operation system. Each Virtual Machine installed on the virtualization software has its own operating system; different operating systems can run on the same hardware. Dedicated Memory and CPU resources get allotted to the virtual machine, so no conflict with another VM which increases the setup cost for Hardware Virtualization. This virtualization type needs a client (native/ web) for management.
Hardware Virtualization examples: VMware ESX / ESXi, Microsoft Hyper-V, Xen Server etc.
2) Software Virtualization/ Type 2 Virtualization:
Vmware workstation Comes here
Here, the virtualization technology application is installed inside a operating System and all Virtual Machines Created can be managed by the application itself. The hardware resources are shared between the host OS (OS in which the Virtualization application is installed) and the virtual machines. The resource changes like memory, CPU or hard Drive allocation are managed easily. The drawbacks of using Type 2 Hypervisor are Shared resources like CPU, Ram, hard disk, Less Stable etc. the over utilization of any of the hardware resources by the VM may cause the Host OS to underperform.
Software Virtualization examples: Parallels Virtuozzo, VMware Workstation, VMware player, Virtualbox etc.