This lecture explores how to calculate the surface area of a solid obtained by rotating a curve around an axis using integrals, focusing on surfaces of revolution. The instructor demonstrates the process of approximating the surface area by partitioning the interval, connecting consecutive points with segments, and rotating them to form an approximation of the true surface. The lecture delves into the calculation of the area of annular regions generated by rotating segments around an axis, emphasizing the importance of partition fineness for accurate approximations. By applying Riemann sums, the lecture concludes with the integral formula for calculating the surface area of a function rotated around an axis, ensuring the continuity of the function for meaningful results.