The switch from analog TV (the traditional TV system using magnetic waves to transmit and display TV pictures and sound) to digital television (the new TV system using information transmitted as "data bits" -- like a computer -- to display movie-quality pictures and sound), is referred to at the digital TV (DTV) transition.
In 1996, the U.S. Congress authorized the distribution of an additional broadcast channel to each TV broadcaster so that they could introduce DTV service while simultaneously continuing their analog TV broadcasts. In addition to improved picture and sound quality, an important benefit of DTV is that it will free up parts of the broadcast spectrum for public safety as well as other valuable uses. This is possible because the modern technology of DTV is more efficient than analog TV technology.
DTV allows the same number of stations to broadcast using fewer total channels (less of the broadcast spectrum) which will free up scarce and valuable spectrum for public safety and new wireless services.