Audio description (AD) is no longer merely a niche interest in the much wider field of audiovisual translation (AVT), itself part of the now vast world of translation studies (TS), but has only relatively recently emerged as an independent field of study and a viable commercial reality in its own right. The time has therefore come for AD to warrant a sizeable volume in which the research work of specialist scholars, the practical applications of service providers, the views of audio description professionals and end-users around the world can come together and provide readers of this Handbook with virtually everything they need to know about the world of audio description. So although this is the first large volume entirely devoted to AD, it is becoming less and less necessary to explain the concept for readers, in the same way that it is no longer necessary to explain subtitling, dubbing, voice-over and other disciplines within the field of AVT (but see Bogucki & Deckert, 2020 and Pérez-González, 2019 for in-depth updated overviews). However, for the record, and according to the American Council for the Blind (https://accessibility.psu.edu/video/audiodescription), audio description is “either live or recorded information, provided by a trained describer that provides descriptions of visual components of an event to become accessible to those who are blind or of low vision”. Or for a more concise, more pithy definition, we turn to Joel Snyder of the Audio Description Project of the aforementioned Council – “the visual made verbal” (see also Snyder, 2008). These definitions, however, need a little filling out. Until recently, very few describers were officially or professionally “trained” (ADLAB PRO, 2017; Chmiel & Mazur, 2017; Perego in this volume). This situation is changing and several contributions in this volume address this question – the figure of the professional describer is definitely taking shape, and the sphere of action of audio description is growing. “Event” is a useful blanket term to cover a whole range of visual phenomena from film, television and many other video products to theatre, to museums, to live events such as football matches or royal weddings. All of these receive attention in the Handbook. And while audio description remains a vehicle to provide access for “those who are blind or of low vision”, other end-users have emerged and continue to do so (see Starr in this volume).