The publication of the first edition of "Introduction to Supersymmetry and Supergravity" was a remarkable success. This second edition contains a substantial amount of new material especially on two-dimensional supersymmetry algebras, their irreducible representations as well as rigid and local (i.e. supergravity) theories of 2-dimensional supersymmetry both in x-space and superspace. These theories include the actions for the superstring and the heterotic string. In addition, a chapter is devoted to a discussion on superconformal algebras in two dimensions and contains an account of super operator product expansion.