This document discusses how rocks behave under different types of stress. It explains that rocks undergo deformation and strain when subjected to tensional, compressional, or shear stresses. The document outlines the different stages of rock deformation, from elastic to ductile to fracture, and factors like temperature, confining pressure, and composition that influence the deformation process. It also describes geological structures like joints, faults, folds, anticlines and synclines that form from rock deformation.