A picture tells more than a thousand words.
Microsoft posted an updated poster which provides a visual reference for understanding key Hyper-V technologies in Windows Server 2012. This Hyper-V poster focuses on Hyper-V Replica, networking, virtual machine mobility (live migration), storage, failover clustering, and scalability.
Microsoft earlier released a Hyper-V architecture poster on Windows Server 8 Beta. To find the differences (are there any?) have a look at this posting.