Heat is energy transferred between substances due to a temperature difference, heat travels from a hot body to a colder body. There are 3 methods of heat transfer Conduction, Convection and Radiation. Entropy is a measurement of how much disorder there can be in a physical system.
Laws of thermodynamics
Zeroth law: if two bodies have reached a thermal equilibrium then if a third bodies comes into contact with them the third body will reach a thermal equilibrium.
Law 1: the internal heat of an object is equal to the heat added.
Law 2: the entropy of a system almost never decreases.
Law 3: at -273.15 degrees Celsius, or 0 Kelvin, the entropy of a system is zero.