VM (Virtual Machine), currently embodied in a product called VM/ESA, is a widely-installed operating system for mainframes from IBM that can host other operating systems, including MVS and Conversational Monitor System (CMS), so that each of the operating systems seems to have its own complete system of software and hardware resources (data storage, telecommunications, processor, and so forth). That is, VM gives each of these operating systems its own "virtual machine." VM, together with CMS, is popular in many large corporations as a system that can let a large number of interactive users communicate or develop and run applications at the same time. VM also provides a good test environment for MVS programs that can be run on an MVS virtual machine.
Many corporations use MVS for business applications and VM as an application development and user communication environment.