If you are referring to server visualization there isn't any AEM related implementation details - the software is installed that same on a virtualized server as it is on physical server.
The other place in AEM where you see the term virtual is around virtual components like the column control components. This is a component that doesn't actual have any code - it exists only to allow the author to drag a particular configuration on the page. Not a lot of documentation about that - you need to dig into the column control code if you want to understand it.
