Returning multiple rows in 8.4

I have users table such as
 create table users(
   user_id   bigserial,
   user_name varchar(50),
   user_surname varchar(100)
 );


how can I write a function to return multiple rows? ( in plpgsql )

what is the return value of the function? records?


and how can i run it without running as select my_func() as (int8,
varchar) ???
is there simple way to do this?

thanks