complex select statement

can someone break this statement down?  what  are the u and pu and p?  is that shorthand for user, parent_user and parent?  if so, what if you had 2 tables with the same first letter? also can you break down the join for me with an example data set?

> $query="SELECT * FROM user u LEFT JOIN parent_user pu ON pu.userid =

> u.userid LEFT JOIN parent p ON p.parent_id = pu.parent_id WHERE

> u.userid = $userid";

>

Yes, those are table aliases and they are set in the query to be shorter, they can be anything you want not just the first letter.  You could do this:

SELECT * FROM user t1
LEFT JOIN parent_user t2 ON t2.userid = t1.userid
LEFT JOIN parent t3 ON t3.parent_id = t2.parent_id
WHERE t1.userid = $userid

thanks!