How does virtualization work?
Generally, server virtualization solutions work by introducing a thin layer over the physical server. This layer partitions the physical server into separate areas that the virtual servers then run on. Computing resources from the underlying server are viewed as a pool of resources which can then be shared among the virtual machines sitting on top. With the exception of that sharing of computing resources, each virtual server acts as its own entity; problems with an application on one server do not affect other virtual machines on that same physical server.