What is "difference of two squares"

n. (context algebra English) The identity $x^2\; -\; y^2\; =\; (x+y)(x-y),$ that holds for all real numbers.

In mathematics, the difference of two squares is a squared (multiplied by itself) number subtracted from another squared number. Every difference of squares may be factored according to the identity

a − b = (a + b)(a − b) 

in elementary algebra.