The document discusses the concept of limits. It explains that as the number of sides of a polygon increases, the area of the polygon approximates the area of the circle it is inscribed in, and the limit of the polygon's area is equal to the area of the circle. It also examines the limit of a function as x approaches 2 from both sides, and defines some fundamental rules of limits, such as the constant rule, sum rule, and multiplication rule. Finally, it outlines several techniques that can be used to calculate limits, including direct substitution, factoring, rationalization, and limits involving infinity and trigonometric, exponential and two-sided limits.