Thomas,
You can also research this question at http://www.vmware.com . To
search the user forums, click on the Communities tab, then 'VMware
Technology Network'.  VMware Server is the newer name for 'VMware
GSX'. That can be confusing when you read old posts that refer to it
by the previous name. GSX has to run on top of a host OS such as
Windows or Linux.  ESX runs on bare metal.

With best wishes,
Keith Arbogast