With the announcement of ESX Server 3.0 and VirtualCenter 2.0 (aka Virtual Infrastructure 3.0) VMware launched a series of whitepapers to clarify technical and marketing aspects of the new offering.
The second one of the series:
This paper describes the architecture of VMware Infrastructure, beginning with the elements that make up its physical topology, followed by the virtual, or logical, view of VMware Infrastructure where the relationships between the virtual architectural elements and the physical world are explored.
Lastly, the architectures of two core VMware Infrastructure components are discussed in further detail.
Strongly recommended. Read it here.