A green screen allows you to record video against a green background so that you can edit the background when producing your video. It’s important you have good lighting when using a green screen so that you avoid unsightly shadows that won’t match up with your edited product.
Green screen can be created fairly inexpensively. In this video, Sam explains how to create your own green screen and lighting setup on the cheap.
Don’t use any green props or green clothing when recording on a green screen.