Foil Method

In Algebra, to multiply two binomials a method is defined called as ‘FOIL’ method. FOIL stands for, first, outer, inner and last term. Here,
First means initial terms of each binomial are multiplied together.

Outer means initial term of binomial is multiplied by second term of other binomial.

Inner means inside terms or Numbers are multiplied, which means first term of initial binomial and second term of other binomial are multiplied together.

Last means final term of both binomials are multiplied.

Let’s see the same with help of variable expression:
(P + Q) (R + S),
=  (P * R) + (P * S) + (Q * R) + (Q * S),
= PR + PS + QR + QS,

Here, PR is first term, PS is outer or outside term, OR is inner term and QS is last term of binomial.
Important thing to remember about Foil Method is that both P ‘first’ term and outside term is both 'P' last and inner term and so on. In this order of all four terms of binomial expression does not matter.