Television is one of the most successful technological consumer products ever produced and has spread to virtually every household in Western society. Television sets are often located in a central part of the main living room. Television viewing is a dominant part of most people's leisure activities and daily lives, and, for many, television has become their most important source of information and entertainment. To say that television has a central place in our culture, or that television over the past decades has thoroughly changed our society and our daily lives is, therefore, an understatement that barely begins to describe reality.
Television, however, is not a static medium, neither as a technology nor as a service. Game consoles, video cassette recorders (VCRs), cable, and satellite systems have already begun to change the image of what television is and what it can be as a medium. In the years ahead, television faces even more radical developments and changes. Terms like interactivity, digitisation, convergence, integrated full service networks, content-on-demand, two-way cables, direct broadcast satellites, the mixture of televisions and computers, of broadcast and Internet, cross media, SMS-TV etc. point out some of the aspects involved in this process of change. Briefly, what is at stake here is the delivery of iDTV services to the home.
But what is ‘interactive digital television’ anyway? The first problem in describing iDTV is the abundance of differing concepts and understandings currently in circulation. The various industrial players in the iDTV field – cable operators, telcos, computer companies, broadcast networks, movie studios, etc. – all seem to have different notions of the concept of iTV as a technology. Furthermore, the players have differing philosophies about what interactivity is and what it means to ‘interact’ with television, as well as varying perspectives on what services and content the consumer will want and be willing to pay for. As a result, during the past decades a broad spectrum of content, services and applications has laid claim to the terms ‘interactive’ or ‘digital television’. Some of them include: multi-channel systems with several hundreds of channels to select from; on-demand access to movies, videos, news, sports; customisation of and control over content; interactive news; local storage of programming; real time interaction and communication between users of the system, such as text messaging, voice telephony or video phone; access to database and online information; voting in (real-time) opinion polls; control over choice of camera angles in the transmission of sports events and the like; interactive games based on stand alone or networked applications; participation in game shows; user created content; electronic town meetings, etc. As should be apparent, iTV is many different things, just as the degree of interactivity varies widely.

Among the variety of challenges confronting iDTV, one of the most urgent is therefore to educate media consumers about what iDTV is, and what kinds of content, services and applications it currently offers and may carry in the future. The following is an attempt at working definitions of the concepts of ‘interactive television’ and digital television’, as well as of the concept af‘interactivity’.
 As indicated, one of the most significant and unique features of new media, compared to the old, is their interactive character. ‘Interactivity’ in this context signifies the active participation of the user in directing the flow of content. Consequently, interactive content designates content types that exchange information with the user, that is, in addition to conventional media’s output to the user, this type of content allows various kinds and amounts of input from the user to the media system, which can significantly influence the form, order, length, or structure of the message – the content of the media text
 Media researchers, especially those from reception research, media ethnography, and media and cultural studies, have in recent years denied the perception of television as a passive medium and have instead pointed out that the viewer’s reading of television texts is always active (and interactive). Practically and technically, however, traditional television claims very little activity from the users. Naturally, the viewers decide what to watch, just as they must cognitively and socially deal with, interpret, and make sense of what they watch on the screen. But apart from this, strictly speaking, the only physical requirements involve turning on the set, (perhaps) changing the channel, and turning it off again (and on the odd occasion making small adjustments to the sound and picture).
 In a negatively defined demarcation, iTV can be understood as television which, aside from the traditional turn-on-zap-and-turn-off interaction, and cognitive (and social) interaction between the presented text and the viewer’s ability to make sense of what is seen – that is, the purely interpretative interaction – also relies upon an actual, physical interaction in the form of choices, decisions and communicative input to the system. In a shorter, more positive version iTV can be considered a new form of television that makes it possible for the viewer to interact with the medium in such a way that he gains control over what to watch, when to watch, and how to watch, or directly opens up for active participation in a programme.
 Understood in this way, iTV can be considered a fairly broadly defined concept. The organising committee for a 1996 world conference on interactive television, The Superhighway Through the Home?, used the term ‘interactive television’:

...rhetorically to suggest the provision of interactive multimedia services to domestic spaces. At its most general this can mean services accessed through a variety of platforms and infrastructures. At its most specific it relates to services and content specifically designed to be used through television, relating strongly in appearance with broadcast style displays and presentation and even co-existing and augmenting existing broadcast programming.

Correspondingly, the Interactive TV News website (no longer available) defined the term ‘interactive television’ as:

...the meeting of television with new interactive technology. ITV is domestic television with interactive facilities usually facilitated through a ‘back channel’ and/or an advanced terminal. Equally important, interactive television is content that users and viewers can interact with via the technical system ... There are many delivery systems, technical standards, possible uses and content. These range from the WWW to home shopping, Digital Video Broadcasting to Internet, movies on demand to video telephony. The unifying factor is that television is central to the entertainment, education, information, leisure and social life of millions of homes all over the world.

In other words, iTV can be defined as interactive services designed for the television, that is, traditional television broadcast combined and coupled with enhancements and extensions that provide viewers with the opportunity to participate in and interact with the content.
 There is no necessary correlation between interactive television and digital television (DTV), if only for that reason that interactive television services have been available for many years over analogue television signals. To mention but two obvious examples, European teletext services have been around for over 20 years and Two Way TV offered analogue interactive gaming services in the United Kingdom as early as 1996. So then what, exactly, is digital television as opposed to interactive television? DTV is first and foremost a technical term that refers to the transition of formerly analogue television technologies to digital technologies. This provides better picture and sound quality and more channels to choose from due to technological and cost-effective advantages. However, for that reason alone that the possibility of broadcasting digital data alongside traditional television picture and programming enables a range of new interactive features, the digitisation of television also, to a considerable degree, expands the potential for interactive services on the television. Thus, with the growing demand for DTV in Europe and around the world, an increasing number of iTV applications are also emerging.