Dustin Spinhirne, Staff Customer Success Architect at VMware, created a short series of Videos, talking about the basic concepts and the architecture of VMC.
The first Part shows the basic concepts:
Part 2 explains the Storage concepts of VMC:
Part 3 covers the, in my opinion, most important bits: The Network Concept.
One thing to keep in mind: all new SDDCs are utilising NSX-T, whereas older SDDCs might have been provisioned with NSX-V.