In this contribution I give a brief introduction to the essential concepts
and mechanisms of decoherence by the environment. The emphasis will be not so
much on technical details but rather on conceptual issues and the impact on the
interpretation problem of quantum theory.Comment: Latex, 16 pages. To be published in the proceedings of the Bielefeld
conference on ``Decoherence: Theoretical, Experimental, and Conceptual
Problems", edited by P. Blanchard, D. Giulini, E. Joos, C. Kiefer, and I.-O.
Stamatescu (Springer 1999
