 In  Section 1  we discuss the concept of suppression of interference and give a simplified survey of the theory, emphasising features that will be relevant later. In fact, the term decoherence refers to two largely overlapping areas of research. The characteristic feature of the first (often called ‘environmental’ or ‘dynamical’ decoherence) is the study of concrete models of (spontaneous) interactions between a system and its environment that lead to suppression of interference effects. The second (the theory of ‘decoherent histories’ or ‘consistent histories’) is an abstract and more general formalism capturing essential features of decoherence. The two are obviously closely related, and will be reviewed in turn.  Section 2  then criticises the claim that decoherence solves the measurement problem of quantum mechanics, and discusses the exacerbation of the problem through the inclusion of environmental interactions. It is thus important to consider not decoherence by itself, but the interplay between decoherence and the various approaches to the foundations of quantum mechanics that provide possible solutions to the measurement problem and related puzzles.  Section 3  deals with the role of decoherence in relation to a number of such approaches, including mainstream foundational approaches such as Everett, Bohm and GRW, traditional approaches such as those by von Neumann, Heisenberg and Bohr, and a few more. Finally, in  Section 4  we describe the overall picture of the emergent structures that result from this use of decoherence, as well as a few more speculative  applications.[1]