Creation of Virtual version of any physical entity is Virtualization . It helps to run multiple operating system as a single entity on a single physical host where a virtualization frame work helps to interrelate between the virtual hardware with physical hardware.
Yes , to run virtual machine we do need a physical hardware, however virtualization is the single most effective way to reduce the IT expenses while boosting the efficiency and agility.
Virtualization helps in increasing the resource utilization , reduction in hardware costing, reduction is capital and operations expenses and providing affordable high availability.
Most common player in Virtualization Technology Companies are :

  • Microsoft : Hyper-V
  • VMware : vSphere
  • Citrix : Xen
  • Oracle : SPARC
  • Red Hat
  • Amazon
  • Google
  • Virtual Bridges : VERDE
  • Promox : KVM , OpenVZ
  • Parallels and many more…

There are various factors which must be considered for hosting multiple VMs on a single host however most important are CPU, Memory and Storage. Time passes by with the change in processing capacity from MHz to GHz , RAM changes from MB to GB and Storage changes from GB to TB for general public. Now even a general public can afford the virtualization technology at low cost and can have a hands-on.
Hyper-V , professional virtualization technology comes as role for free in bundled package of Server Operating System as well as freely available in Core [Non-GUI format] . You can download ISO of Hyper-V core from Microsoft official site and can install to enjoy virtualization. The drawback is No-free licenses for VM running on it and No Graphical interface.

ESXi ,professional virtualization technology package provided by VMWare for free as trial version for limited time frame [default 160 Days]. However you can enjoy the virtualization technology as an application on your laptop or desktop by installing VMWare Workstation .

Virtualization technology is either available for free in open-source world or its free for limited time-frame in the commercial world . In a way or other you have technology in your hands to experiment , understand ,learn and to work on . The time has come to know the matrix.