Duality,

As everyone mentioned above. A Virtual Dedicated or Private Server is pretty much a mini Dedicated Server on a Server where the Server has been partioned into smaller chunks and allocated part of the Hard Drive and Memory whilst the CPU is shared Equally.

Control Panel's for example cPanel tend to be cheaper for a VPS Cpanel License hence if you want to become a distributor you need approx. 150 VPS Licenses. That's why someone like FDCServers can provide a good Spec VPS with cPanel Free for $39.00 per Month.

A Dedicated Server is just one which is Dedicated to you and not shared with anyone else.

Hope this Helps.