When a 4 : 3 image is displayed on 16 : 9 display, there are a number of ways to display the image. The way it is displayed is usually adjustable in the television's set up menu.
To show the complete image, the height of the image will fill the screen. The left and right edges will be left blank.
To fill the width, the image can be increased in size so the top and bottom of the image will be lost. Some televisions have set up adjustments to allow the image to be moved up and down to recover upper or lower parts of the image. That can be useful for programs such as sports coverage where the scores and clocks are at the top of the image, for example. The menu setting will be seen as "Zoom" and possibly an additional control of "Move"
The image can be stretched so that the 4 : 3 image will fill a 16 : 9 screen. The result is that the whole image is wider than it was originally. The menu setting is normally "Stretch". Sometimes the amount of stretch might be adjustable.