VMware

        VMware's desktop software runs on Microsoft Windows, Linux, and Mac OS X, while its enterprise software hypervisors for servers, VMware ESX and VMware ESXi, are bare-metal hypervisors that run directly on server hardware without requiring an additional underlying operating system.

VMware has produced two virtualization products for servers:

1. VMware vSphere(also called "ESXi"), an enterprise-level product, can deliver greater performance than the freeware VMware Server, due to lower system overhead. VMware ESXi, as a "bare-metal" product, runs directly on the server hardware, allowing virtual servers to also use hardware more or less directly. In addition, VMware ESXi integrates into VMware vCenter, which offers extra services
2. VMware Server (formerly called "GSX Server"; obsolete as of 2011) was also provided free of charge for non-commercial use, like VMware Player, and can also set up virtual machines. As a "hosted" application, VMware Server runs within an existing Linux or Windows operating system.