HDTV provides a much wider screen than conventional television.  Because, the viewing area format is similar to a movie theatre screen, the left and right edges of movie presentations don't need to be chopped off.  The HDTV  wide screen format provides a more intense viewing experience by taking full advantage of the actual human field of vision.

The dimensions of a television screen is referred to as the aspect ratio.  The HDTV television format uses an aspect ratio of 16:9.  By comparison, the aspect ratio used by conventional television is almost square (4:3 ratio).

While most theatrical movies have used the wide screen format for years, most television programs (until now) have been produced using the old 4:3 narrow screen format.  Consequently, when purchasing a High Definition television, it is important to select a model that can displays old television shows without distorting the picture or wasting screen "real estate".  Most high definition sets will allow the viewer to select from a variety of display formats.  For example, one format will display the legacy television program with a dark area at both the left and right sides of the screen.  Another format will crop the top and bottom portions of the television program.  More sophisticated technologies will stretch out the 4:3 images horizontally with minimal picture distortion. 

Presuming that we will continue to enjoy reruns of "I Love Lucy" and "Friends" for years to come, it is important to consider this issue prior to making a purchase decision.