Some basic notions and laws of thermodynamics are reviewed. The characterization of equilibrium states via extremal principles of energy, entropy, and various free energies is discussed, together with the existence of equations of state between the thermodynamic variables. Various response functions are discussed, and restrictions on their range of values are established as conditions for the stability of a thermodynamic system in equilibrium. Various transformations between states are considered, including a short discussion of some more practical considerations regarding the working and utility of cyclic transformations as operating machines. The simple case of an ideal gas is used often as an example of the various concepts and physical quantities reviewed or introduced.