In present, technology is growing, many medium is appeared. And television is changed. So the term, television isn't same as past. The narrowcasting that became common to television during the multi-channel transition has thus required adjustments in theories about the mass nature of the medium, while the exponential expansion in viewers choice and control since the network era has necessitated an even more substantive reassessment of television. Taking up these issues, this chapter provides an overview of some of the central ideas that have governed the study of television and culture as well as some preliminary tools for making sense of television in the post-network era.
Defining television is difficult in nowadays because of change of television and other medium. Television means everything connected with television. A television is not just a machine, but also the set of behaviors and practices associated with its use. In 1940's when television first entered homes, radio had to changing. Today, radio steal alive. In same ways, in recent years, as the television experience has encompassed new capabilities and spread to additional screens. But television may no be dying, but changes in its content and how and where we view have complicated how we think about and understand its role in the culture. But we can't avoid the argument about ways of thinking about television. But in the network era, there was no need for esoteric discussions of what is television as it was assumed to be a simple technology whose variation spanned little more than screen size and color or black and white. In 1960's, foundational understandings of television view it as a-if not the-central communicative and cultural force within society. Low barriers to access greatly contributed to its cultural importance in the network era. Network-era norms imposed the synchronicity of linear viewing, and television earned its status as an instigator of water-cooler conversation by providing shared content for discussion. Television is cultural institution. And at the same time, television is cultural industry. Television industry workers may primarily make decisions based on what types of programming they perceive to be most profitable, yet these decisions still have important cultural implications for what stories are told, by whom, and how society comes to understand the worlds that television presents. So television is imperative: in the cultural industry of television, business and culture operate concurrently and are inextricable in every aspect. the breadth of the audience reached by network-era programming allowed television to circulate ideas in a way that asserted and reinforced existing power structures and dominant ways of thinking within a society. television programs provide a cultural forum to negotiate ideas within society makes sense insofar as television continued to facilitate this cultural role after the network era on certain occasions; broad and heterogeneous audiences now rarely share individual programs in the manner they assumed. Because audiences are now more narrow and specialized.
Televisions transition from its network-era norm as a mass medium toward its post-network-era function as an aggregator of a broad range of niche and on-demand viewing audiences has required significant adjustments to industrial assumptions about the medium. Post-network-era practices have led the television audience not only to fracture among different channels and devices, but also to splinter temporally. The control over the television experience that various technologies offer has ruptured the norm of simultaneity in television experience and enabled audiences to capture television on their own terms. New devices have provided tools to capture television and consequently have produced a norm of asynchronous viewing that has altered the interaction of the culture with the medium in crucial ways.

Since post-network era, television industry changed significantly. The most noteworthy adjustment evident by 2005 was the erosion of televisions regular operation as a mass medium. It was already apparent that we needed to reassess television and see it as a medium that primarily reaches niche audiences. Joseph Turow considers the process through which this industry transitioned from mass market publications with titles such as Life, Look, and the Saturday Evening Post to more narrowly targeted magazines and argues that demand from advertisers to reach ever more specific audiences fueled the fragmentation. The redefinition of television in the course of the multi-channel transition as a medium that supports fragmented audiences and polarized content consequently has exacerbated the cultural trends and outcomes that Turow identified in the magazine industry.