Widescreen usually refers to the aspect ratio of an image. In general terms, most images are considered to be in widescreen format when they have an aspect ratio larger than 4:3.

When talking about widescreen, generally, most people are referring to the aspect ratio or shape of their TV set, monitor or digital image. One of the best ways to understand widescreen is to compare it with the most common type of aspect ration, 4:3 which is the aspect ratio or shape of a standard TV set.

A standard TV set is pretty much boxy in shape. The aspect ratio is 4:3, this means that the TV screen is 4 times wide by three times high. Because this ratio is almost equal to each other, it is considered similar to a box or square. A perfect square would be 4:4, which is really a ratio that is to 1:1.Widescreen

So now that we know that a standard TV is boxy or squarish in shape having an aspect ratio of 4:3, widescreen formats usually have 16:9, a much more rectangular shape. A rectangular is a much more natural looking image. When the human eye sees the world, it does not see a box, but mainly a panorama image. We might focus our attention on a square shape in front of us, but there is a lot more visual information that our peripheral vision picks up. 16:9 aspect ratio is considered widescreen format and is much more natural to view.

Most cinematic films are an aspect ratio of 16:9, so they can be viewed easily on a widescreen TV or monitor. You might not have realized that when you watch a movie on your standard TV that has an aspect ratio of 4:3, part of the sides of the movie are cut off or cropped. When you watch a movie on a widescreen, you are able to see the entire picture without any cropping. Sometimes widescreen is referred to by the term "letterbox" meaning a rectangular shape.