Sql_Handle and Plan_Handle Explained

For batches, the SQL handles are hash values based on the SQL text. For database objects such as stored procedures, triggers or functions, the SQL handles are derived from the database ID, object ID, and object number. plan_handle is a hash value derived from the compiled plan of the entire batch.

http://blogs.msdn.com/b/sqlprogrammability/archive/2007/01/09/2-0-sql-handle-and-plan-handle-explained.aspx