This question may be a bit unusual but I think it's an interesting angle:
Why does a remote desktop connection to my server with all four of my 30 inch (@2560x1600) monitors work, even though the server doesn't have a graphics card installed? I guess the graphics are perhaps not really rendered on the server? What exactly happens there so that this works?

Searching for this I mostly found "how to enable multi monitor support" but not an answer to my question yet.

Any links/documentation I can read to understand this better?

(To get all four monitors working well on my local machine the one graphics card I had wasn't even enough, so I have two graphics cards on the local machine now)

The operating systems are Windows 7 home premium and it's a Windows Server 2008 R2.