A ring binder is a type of folder used to organize and store loose sheets of paper. It consists of a cover, usually made of cardboard or plastic, and a mechanism with metal rings that can be opened and closed. This allows users to add or remove pages easily, making it a popular choice for students and professionals alike. Ring binders come in various sizes and colors, accommodating different paper formats such as A4 or letter size. They can also hold dividers, which help categorize information, and are often used in conjunction with sheet protectors to keep documents safe from wear and tear.