This document provides an introduction to heat transfer from Dr. Jitendra B. Chaudhari of the Department of Mechanical Engineering at R. N. G. P. Institute of Technology. It defines heat as the average kinetic and potential energy of molecules in a substance, which can be measured by temperature. It then describes the three modes of heat transfer - conduction, convection, and radiation - including their mechanisms, applicable phases of matter, governing laws, and key parameters. Conduction involves lattice vibration and free electrons in solids. Convection involves molecular motion and collisions in liquids and gases. Radiation involves electromagnetic wave transfer without molecules.