I am going to suggest MSDN, because it is a good resource. All the DMVs are well documented there. Start with sys.dm_exec_cached_plans and have a look at all related DMVs.
Again, the plan handle is just a binary identifier. It just identifies a plan.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability