First Timer Question About SWQL

Hello, I am a DBA and this is my first venture into SWQL.  I am trying to figure out why some queries are running so slow but I cannot figure out what this query is actually doing.  I have been reading some about SWQL and I have yet to figure out the relationship(s) and how to decipher them.  Can anyone help me figure out what this query is actually doing?  I think if I can get through this one, I might be able to backtrack to figure out another one.  Here is the query:

SELECT Node.PCUs.FirmwareVersion
FROM Orion.Nodes Node
WHERE Node.PCUs.PollState   @pollstate
AND NodeId = @nodeid
RETURN XML RAW (pollstate=3, nodeid=2617)