In Fahrenheit 451, a form of interactive television has taken the place of reading, intellectual discussion, and critical thinking. In Guy and Mildred's home, three walls of their parlor have been replaced by wall-sized screens to give the feeling of full immersion, though Mildred insists that she must have the fourth wall so she can feel fully immersed.
Mildred's favorite program, which she refers to as her "family," is more or less a simulation of real life. In the context of the story, television programs like Mildred's "family" are symbolic of hollow or shallow entertainment that makes people feel good and requires no thinking. The irony is that in order to escape the complexities and unpleasant aspects of life, people have chosen to hide in a simulation of real life. Ultimately, conveniences like television help them to hold on to the illusion that everything is perfect the way it is, despite the horror that is occurring outside their homes. This is why Mildred reacts so strongly when Guy destroys the television walls; he is essentially trying to destroy the illusion.
Throughout much of his life, Bradbury was ambivalent about television. He recognized that it had the potential to tell engaging and thought-provoking stories, but felt that most of what people watched was shallow entertainment. He was also concerned that television would replace reading and dialog. In Fahrenheit 451, Bradbury's description of television isn't far off from the present-day reality shows. Like Mildred's "family," modern reality television implies that it is a realistic portrayal of life and culture, but it is rarely doing either. Moreover, the popularity of reality television suggests that, rather than go out and live life, many people prefer to watch a simulation of life on TV because it's easier.