A family of hypersurfaces evolves by mean curvature flow if the velocity at
each point is given by the mean curvature vector. Mean curvature flow is the
most natural evolution equation in extrinsic geometry, and has been extensively
studied ever since the pioneering work of Brakke and Huisken. In the last 15
years, White developed a far-reaching regularity and structure theory for mean
convex mean curvature flow, and Huisken-Sinestrari constructed a flow with
surgery for two-convex hypersurfaces. In this course, I first give a general
introduction to the mean curvature flow of hypersurfaces and then present joint
work with Bruce Kleiner, where we give a streamlined and unified treatment of
the theory of White and Huisken-Sinestrari. These notes are from summer schools
at KIAS Seoul and SNS Pisa.Comment: Lecture notes based on arXiv:1304.0926 and arXiv:1404.233