I will discuss the nature of equilibrium states and the origin of the time asymmetric evolution of macroscopic systems, as embodied in the second law. There are on the conceptual level, strong similarities as well as important differences between classical systems, whose microstates evolve according to Hamiltonian dynamics, and quantum systems, whose wave functions evolve according to the Schrodinger equation. I will also examine the notion of typicality of microstates of a specified macrostate in the classical/quantum context.