Any func/proc can go into a package.
Func/proc are 'invisible' when they are private func/proc.

example:

create or replace package junk is
PROCEDURE do_nothing;
end junk;

create or replace package body junk is
FUNCTION my_private_func RETURN BOOLEAN IS
BEGIN
RETURN TRUE;
END;

PROCEDURE do_nothing IS
BEGIN
NULL;
END;
end junk;