The document discusses absolute value, absolute value equations, and absolute value inequalities. It defines absolute value as the distance from zero on the number line, which is always positive. Absolute value equations account for both positive and negative cases, while absolute value inequalities split into two cases - one for positive values and one for negative values. An example shows how to write the inequalities for both cases of |x| < 4, determine the solution is an intersection of the cases, and represent the solution set as {x | -4 < x < 4}.