Heat in Physics is an energy that is in a process of transfer between a system and its surroundings other than the transfer of matter. In Thermodynamics, a science that deals with the study of heat and temperature and their relationship to energy and work, finer details of the process is unpredictable. Heat flows from a hotter to a colder body when there is a physical pathway. This pathway is suitable and can be direct such as radiation and conduction. It can also be indirect as in convective circulation.
There are three types of heat transfer or heat propagation; conduction, convection and radiation. Heat transfer is the process by which heat projects externally however, depending on the temperature and pressure. Also called the movement of heat from a low temperatured state which increases as heat progresses.
Conduction is the heat transfer by contact, immediate contact.
Convection is the transfer of heat through air and water.
Radiation is the transfer of heat regardless of the presence of atoms or particles.