The experimental and theoretical progress in understanding the electronic structure and the related parameters of Schottky interfaces and heterojunctions is reviewed. Particular emphasis is devoted to the solution of several historical controversial points, to the impact of novel ab initio theoretical approaches, to new experimental techniques based on synchrotron light and free electron lasers, to the efforts towards controlled modifications of interface parameters and to the foreseeable future developments of this vigorously progressing and:technologically crucial field.