This text aims to provide an informal, readable introduction to the basic ideas of thermal physics. It is designed to make the reader feel comfortable with the principles of entropy and free energies. There is a repeating theme: molecules (spins) do X to maximize their entropy, and molecules (spins) do XX to minimize their free energy. This finally leads to the idea of the Landau-Ginzburg free-energy functional. The author describes two examples from phase transitions. This book should be of interest to undergraduates in physics, materials science, materials engineering and physical chemistry.