To explain what variables are, why and how they are used, and how to isolate them in equations (i.e. how to solve a one-variable algebraic equation.) This slideshow also introduces coefficients as well as the algebraic "shorthand" ways to signify multiplication and division.
I would consider this a good packet for someone who is preparing to begin study of algebra or has not done any algebra in a long time. Assumes a solid understanding of arithmetic but NO prior knowledge of algebra.