I think you mean FOIL, not FIOL. Actually, it wouldn't affect your answer if you performed FIOL in that order, but FOIL is the usual order.
(a+b)(c+d) is the product of 2 binomials, and that is the purpose of FOIL>
Mult. together the FIRST terms: obtain ac. Next, multiply together the outer terms: obtain ad. Next, multiply together the inner terms: obtain bc. Finally, multiply together the last terms: bd. Result: ac+ad+bc+bd.
