HDTV picture shape is the same like a modern movie

What does “aspect ratio” mean?

Aspect ratio is a measurement of the width of the TV picture in relation to the height. The traditional TV picture has an aspect ratio of 4 by 3 denoted as 4:3. That means a picture with a 40-inch width would have a height of 30 inches. It’s almost square. An HDTV
picture has a wide-screen picture, with an aspect ratio of 16 by 9 or denoted as 16:9. If you get out your ruler, you realize that it is almost twice as wide as it is high. Incidentally, it’s the shape of a movie picture at the cinema.