  We give a short, critical review of the issue of decoherence. We establish
the most general framework in which decoherence can be discussed, how it can be
quantified and how it can be measured. We focus on environment induced
decoherence and its degree of usefulness for the interpretation of quantum
theory. We finally discuss the emergence of a classical world. An overall
emphasis is given in pointing at common fallacies and misconceptions.
