The two types of server virtualization available today are Virtual Dedicated servers and Virtual Private servers.  Below we will discuss the differences and similiarities of the two.

Differences:

Virtual Dedicated: 
Hardware based virtualization that does not share the kernel and as such is more secure than Virtual Private (VPS).  Virtual Dedicated can also assign a "guaranteed" or reserved amount of CPU from the hardware whereas VPS uses clock cycles for it's resource allocation.

Virtual Private:
Software based emulation that does share the kernel and is less secure than Virtual Dedicated.

Similarities:
Both allow the sharing of one physical system for hosting multiple separate virtual operating systems.

Conclusion:
3Essentials utilizes Virtual Dedicated Servers in it's solutions due to the increased security and the closer relationship that Virtual Dedicated has to true dedicated servers.  Virtual Dedicated Servers from 3Essentials look and feel just like a dedicated server and provide the same level of redundancy as that of a high end server without the high end price.