Pros
Some of the pros of green screens are you are able to put any image or video on a green screen. Another pro is any camera works with a green screen you don't have to get a high tech camera. Also green screens are inexpensive and they save lots of money because back in 1920 you would have to use boards with pictures on it which was very expensive when you have about thousand. With green screens you can use it to look like you are on a mountain or you falling in a ditch that is only 3 feet deep in real life
Cons
Some cons are you cant where green while making videos with the green screen. If there are wrinkles in the green screen the green screen doesn't get the image on correctly. You need lots of technology to get the green screen to work and you also need high tech lights. You need lot and lots if green screen to be able to make a movie with amazing special effects.