This book is an informal, readable introduction to the basic ideas of thermal physics. It is aimed at making the reader feel comfortable with the extremum 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 illustrates how powerful the idea is by using two examples from phase transitions.