Zeroth Law of Thermodynamics

This principle of heat transfer forms the basis of comparison between temperatures. This law operates by three equal systems. Three systems are required, because heat can only transfer when an intermediate medium is involved. That intermediate medium may be a solid, a gas or a liquid.

The First Law of Thermodynamics

Energy changes form and moves from one position to the next position, and energy is always constant. According to this first law of thermodynamics, energy causes heat transfer from the hotter object to the cooler object to remain constant, and whatever heat is lost during the process is turned into another form of energy.

The Second Law of Thermodynamics

When heat is transferred or transformed, it becomes less useful. When heat is being transferred from one object to a cooler item, eventually the thermal energy will be used up during the process.

Methods

Heat transfers via three primary methods. Conduction is when heat moves from one object to another. Convection is when heat moves in currents through a gas or liquid. Radiation heat transfer occurs through the use of electromagnetic waves.

Process

When heat transfers from an item, it will transfer to the coolest object first. Also, heat doesn't transfer in a linear path. Instead, it radiates in all directions until it reaches the object that will store its energy.

Source:

Hyperphysics: "Thermal Equilibrium"

NASA: "First Law of Thermodynamics"

Efunda.com: "Basics of Heat Transfer"