The document discusses mathematical expressions and algebraic expressions. It provides examples of algebraic expressions like 3x^2 - 2x + 4 and explains how to perform operations on polynomial expressions, like factoring 64x^3 + 125 as (4x + 5)(16x^2 - 20x + 25). The key purposes of factoring polynomials are stated as making it easier to calculate outputs, simplify rational expressions, and solve equations. An example is given to evaluate the factored expression 2x^3 - 5x^2 + 2x for various values of x.