A green belt is a type of belt that is usually worn around the waist. It is usually green in color and is usually made of fabric like nylon or cotton. Someone might wear a green belt for a variety of reasons, such as fashion, exercising, or even martial arts. Most people who wear green belts in martial arts are advanced student. They usually wear the belt to show that they are more experienced and have practiced more than the students who wear white or yellow belts.