It's difficult to put that in context, however I guess that it just needs to categorise the environment than it is running within (in this case, basically a single user operating system environment). A physical desktop PC (workstation) would appear to a running program as (basically) similar to a virtual workstation (running as a terminal server session). A program might want to make that distinction for licensing purposes, for instance.
It probably does not mean that your PC IS running as a terminal server. However it could be.
To check, go to "System Properties", go to the "Remote" tab, and you will find the settings in the lower half of that panned ("Remote desktop").
Having that turned on would allow you to connect to the desktop of your PC remotely (other settings on routers etc would be needed as well). When a remote user is logged in, the physical desktop is locked. Most home users would not have use for this - unless you understand what it is and really need it, leave it off...
Edited by x64, 09 July 2014 - 01:09 AM.