A "Green Screen" is a special effects technique used in film and photography. It involves a bright green backdrop that can be replaced with different images or videos during editing. This allows filmmakers to create various environments without needing to physically be in those locations. The green color is chosen because it is distinct from most skin tones and clothing, making it easier to isolate the subject. This technique is widely used in movies, television shows, and even video games to create immersive scenes, such as those seen in Hollywood blockbusters or news broadcasts.