I want to start out by saying I am not sure about the origin of this query. I use it frequently to find activity on my servers. I left some of the code commented to show a few example items you can add and additional search criteria. I really encourage anyone to grab a query and alter it to show information useful to them.
It uses sys.dm_exec_query_plan() (via inline select forgive me) to grab the query plan when possible. Additional information to grab performance information and SQL code executing uses these DMVs sys.dm_exec_requests, sys.sysprocesses and CROSS APPLY sys.dm_exec_sql_text(). Use the links to see the information being returned.