Numeric expressions contain only numbers, while algebraic expressions contain variables that represent unknown numbers. An algebraic expression has three parts: a variable, a coefficient, and a constant. A monomial is an algebraic expression with only one term, while a polynomial has two or more terms. To evaluate an algebraic expression, substitute values for the variables and simplify using order of operations. Expanding an expression uses the distributive property to multiply terms within parentheses. Simplifying combines like terms, which have the same variables raised to the same powers.