The document defines lateral limits and explains how to determine if a limit exists based on the equality of the left and right lateral limits. The left lateral limit is the limit as x approaches a from the left, written as lim f(x). The right lateral limit is the limit as x approaches a from the right, written as lim f(x). If the left and right limits are equal, then the overall limit exists. Otherwise, the limit does not exist. Examples are provided to illustrate this concept along with exercises for practicing evaluating limits laterally.