A virtual server is a portion of resources within a physical server that forms a machine or separate server, reserving this portion of resources for its use by taking advantage of existing technologies of Multi Core Processing and RAM capacities. It has its own operating system and attributes. We can also say that the physical server can have an operating system created solely to manage virtual machines allowing a more efficient use of the resources. The virtual server can have the operating system you want. Virtual servers can vary, according to the number of cores assigned, as well as RAM and storage capacity.