What is the difference, if any,between a virtualmachine and a world?

What is the difference, if any,between a virtualmachine and a world?

A.
Each virtual machine contains one or more worlds.

B.
Virtual machines supports Windows and Linux, worlds support FreeBSD.

C.
Virtual machines run inside worlds and under the VMkernel.

D.
The terms "virtual machine" and"world" mean exactly the samething.