Imagine that you have a really big picture you want to show on your TV. But the picture is so big that it won't fit on the TV screen all at once. What do you do? You can either make the picture smaller so it fits on the screen, or you can zoom in on the picture so you can see more detail even though you can only see part of the picture at a time.
A zoomed video port is like zooming in on a picture. When you play a video on your computer or TV, the video is made up of lots of little dots called pixels. When you plug your computer or TV into another device like a camera or gaming device, the two devices need to communicate with each other to make sure the video looks good. The zoomed video port helps the devices talk to each other and make sure that the video is always zoomed in the right amount, so that you can see everything you're supposed to see and nothing is cut off.
It's like having a special helper who makes sure you can see all the important parts of the video, even if the video is too big to fit on the screen all at once.