This lecture covers the concepts of curvature and oriented curvature of a regular curve, explaining how the direction of the tangent vector changes and how to formalize the intuition of a curve being more curved at a point. It also discusses the associated tangent and unit rectifier field, as well as the monotonically increasing nature of curvature. The lecture delves into the definition of oriented curvature, the positive basis formed by tangent and normal vectors, and the formula for inflection points.