This lecture covers the theory of plates, focusing on the framework for the theory of plates, variation of bending and stretching energies, and the Föppl-von Kármán Equations. The lecture delves into the interpretation of mean and Gaussian curvatures of a surface, the curvature tensor, and the principal curvatures. It also discusses the significance of Gaussian curvature in surfaces and the impact of nonlinear strain on the deformation of thin elastic plates.