The document discusses continuity and discontinuity of functions. It defines a function as continuous at a point if it satisfies three conditions: 1) it is defined at that point, 2) the limit as it approaches the point exists, and 3) the limit equals the function value at that point. It gives an example of checking continuity at a point. It then defines three types of discontinuity: removable discontinuity where the limit does not equal the function value, jump discontinuity where the left and right limits do not match, and infinite discontinuity where the limit is infinite.