A link and pin coupler is a type of coupling device used primarily in railway systems to connect two train cars. It consists of a link that is attached to one car and a pin that fits into the link on the adjacent car, allowing for a secure connection while enabling some movement between the cars. This coupler design is simple and effective, providing a reliable way to join multiple train cars together. It is commonly found in older railway systems and is known for its ease of use, although modern systems often utilize more advanced coupler designs for improved safety and efficiency.