Thermodynamics simply describe's how thermal energy is changed to and from various forms of energy and how it affects matter. It is extending the physics that deals with the relationships between heat and other forms of energy.
Thermal Energy is when Temperature causes a substance or system to gain energy, the energy of moving or vibrating molecules. There are multiple systems in Thermodynamics which includes a massive amount of measuring this energy in the different systems, there are large numbers of atoms and or molecules that have major effects on each other in complicated ways. But, if these systems meet at the right criteria, which is called equilibrium, they will then be able to be described with a very small number of measurements or numbers. This is often idealized as the pressure of the system, mass of the system and the volume of the system, or some other equivalent set of number.
Heat. Some Days it can be a blessing, others it can be a total pain. But the way heat travels might be a tad bit different than the way you expect it to be. The heat is transferred between substances and or systems due to difference of the temperature of both of the substances. For example, it's pretty much putting frozen chicken into the oven, it's cold when it goes in, but once it comes in contact with the heat, it begins to become hot because Heat is also a form of energy, which means that it is conserved, but it cannot be created or destroyed because of this.
Heat can easily be transferred from one body to another or between a body and the environment, by three different means: Conduction, Convection, and Radiation.
Conduction: Conduction is energy transfers through a solid object. Conduction that happens between bodies occurs when the bodies are in direct contact, and the molecules transfer energy across the interface.
Convection: Convection is when heat is transferred to form a fluid medium. Molecules in a gas and or liquid come within contact with a solid body transmit or absorb the heat from or to that body and then move away, allowing all the other molecules to move into the correct placing and repeat the process. The efficiency can be improved by increasing the surface area to be cooled or heated, as a radiator, and b y forcing the fluid to move over the surface, as with a fan.
Radiation: Radiation is the discharge of electromagnetic energy, particularly infrared photons that carry energy of heat. all matter absorbs and emits some electromagnetics radiation, the net amount of which determines whether this causes a gain or loss in heat.
The Four Laws of Thermodynamic
The Zeroth Law: The Zeroth Law states that if two bodies have no heat flowing between them when they are connected by a path permeable to heat with some third bodie, then they are also equilibrium with each other. This establishes temperature as a fundemental and measurable property of matter.
The First Law: The First Law states that the total increase in the energy of a system is equal to the increase in thermal energy plus the work done on the system. This concludes that heat is a form of energy and is a subject to the principle of conservation.
The Second Law: The Second law states that heat energy cannot be transferred from a body with a decreased body temperature, to a body with a increased body temperature without the addition of energy. This is the whole reasoning behind why we need to pay to run an air conditioner.
The Third law: The Third Law states that the entropy of a pure crystal at absolute zero, is zero. As explained before, entropy is also called "waste energy," energy that is not able to do work, and since there is no heat energy at all at absolute zero, there therefore cannot be any waste energy. Entropy is also a measure of the disorder in a system, and while a perfect crystal is defined perfectly ordered, any positive value of temperature means there is motion inside the crystal, which causes disorder. For these various reasons, there can't be and won't ever be any physical system with lower entropy, so entropy will always have a positive value.
Therefore Thermodynamics has a greater science behind it than expect. It's not just another one of out many scientifical words, well it is, but it has a very larger amount of detail behind it.