Virtualization is a term that refers to the abstraction of computer resources:
* Virtual machine (VM), a software implementation of a machine (computer) that executes programs like a real machine
o Platform virtualization, which separates an operating system from the underlying platform resources
+ Full virtualization, sensitive instructions replaced by binary translation or trapped by hardware - all software can run in the VM, e.g. IBM's CP/CMS, VirtualBox, VMware Workstation
+ Hardware-assisted virtualization, CPU traps sensitive instructions - runs unmodified guest OS; used e.g. by VMware Workstation, Xen, KVM
+ Partial virtualization, for specific applications rather than the operating system
+ Paravirtualization, a virtualization technique that presents a software interface to virtual machines that is similar, but not identical, to that of the underlying hardware, thereby requiring guest operating systems to be adapted, e.g. Xen in early stage
+ Operating system-level virtualization, a method where the operating system allows for multiple user-space instances (virtual hosting, chroot jail + resource management)
o Application virtualization, the hosting of individual applications on alien hardware/software
+ Portable application, a computer software program that runs from a removable storage device as a USB flash drive
+ Cross-platform virtualization, allows software compiled for a specific CPU and operating system to run unmodified on different CPUs and/or operating systems
+ Virtual appliance, a virtual machine image designed to run on a virtualization platform
+ Emulation or simulation
* Virtual memory, which allows uniform, contiguous addressing of physically separate and non-contiguous memory and disk areas
* Storage virtualization, the process of completely abstracting logical storage from physical storage
* Memory virtualization, aggregates RAM resources from networked systems into virtualized memory pool
* Network virtualization, creation of a virtualised network addressing space within or across network subnets
o Virtual private network (VPN), a computer network in which some of the links between nodes are carried by open connections or virtual circuits in some larger network(s), such as the Internet
* Desktop virtualization, the remote manipulation of a computer desktop
* Data virtualization, the presentation of data as an abstract layer, independent of underlying database systems, structures and storage.
* Database virtualization, the decoupling of the database layer, which lies between the storage and application layers within the application stack
