What is your problem?
If you watch a TV channel that broadcasts in 16:9 (large movie format) on a television with a 4:3 format (the traditional television format), the image will be distorted. With black horizontal or vertical bars, you can adapt the format of the TV image to that of your screen.
Is the image stretched vertically? This is because the TV channel concerned broadcasts in 16:9 and you have a 4:3 screen.
With the black horizontal bars, your 4:3 screen resembles a 16:9 screen and the image is no longer
distorted.
Is the image stretched horizontally? This is because the TV channel concerned broadcasts in 4:3 and you have a 16:9 screen.
With the black vertical bars, your 16:9 screen resembles a 4:3 screen, and the image is no longer
distorted.