This technique is also referred to as colour keying, colour-separation overlay (CSO; primarily by the BBC), or by various terms for specific color-related variants such as green screen, and blue screen – chroma keying can be done with backgrounds of any color that are uniform and distinct, but green and blue backgrounds are more commonly used because they differ most distinctly in hue from most human skin colors. No part of the subject being filmed or photographed may duplicate the color used as the backing. Wikipedia
This an awesome way to have a professional actor/spokesperson advertise your business without the cost of hiring someone to actually do the filming. The green screen is replaced with your own image or video … storefront, office, products, beautiful mountains, etc. Personalize the video to make it yours.