Thermal energy is the energy possessed by objects due to the movement of particles. Heat is a form of energy that is transferred as thermal energy moves. There are three main modes of heat transfer: conduction, convection, and radiation. Conduction involves heat transfer through direct contact between objects. Convection involves the circulation and movement of heated particles in fluids like liquids and gases. Radiation involves the emission of electromagnetic waves and can occur through a vacuum without direct contact between objects.