Here is another PDF I found very useful. It provides an edition overview, licensing overview, info on CALs and how to transition to the new licensing model.
Datacenter edition for highly virtualised private cloud environments
Stanard edition for non or very small virtualised environments
Essentials edition for small businesses up to 25 users on up to two processors
Foundation edition for small businesses up to 15 users on single processors
CALs are still required for every user or device accessing a server
Consistent processor-based license
If you are an Microsoft SA customer check your entitlement as you may already have access to Server 2012!