This chapter considers the evidence for implicit learning in different domains, how implicit learning may best be modelled, its relationship to neuropsychology, and its practical implications. It focuses on the manner in which implicit learning and implicit knowledge are best conceptualised in general. The chapter presents the possible relationship between implicit learning and similar constructs and discusses some specific frameworks for understanding implicit learning. Specificity of access has been one of the most important criteria of implicit knowledge. The knowledge underlying perfomance on numerous tasks is not elicited by a free recall test; the knowledge is more accessible on forced-choice tests; finally, it often fails to transfer to different tasks involving conceptually irrelevant perceptual changes. Implicit and explicit learning are likely to be distinct modes. The chapter also presents some closing thoughts on the key concepts discussed in the preceding chapters of this book.