When you multiply a difference of two squares, why is your answer a binomial instead of a trinomial like when you multiply the sum of two squares

Difference of two squares:

(a+b) (a-b) = a² - b²

(a-b) (a+b) = a² - b²

The difference of two squares results to a binomial because the middle term cancels each other out.

example:

a = 2; b = 3

(2 - 3) (2 + 3) = 2 (2+3) - 3 (2+3) = 4+6-6+9 = 4 + 0 + 9 = 4 + 9