what does this do - Mailing list pgsql-sql

Hi,
I have a piece of python code that excutes a SQL statement:

apitempCur.execute("select * from jfcs_balancedue('%s') f(enrolleeid varchar, 
course_cost decimal, paid_amt decimal)" % (enrollIds,));

The "enrollids" is a list of primary keys and the "jfcs_balancedue" is a user 
defined function.  What I don't understand is the "f(enrolleeid 
varchar, ...)"   I have no idea what it's for?  Would some kind soul educate 
me.

Thanks in advance,
Jhnf