A zipper is a device used to connect two pieces of fabric for easy opening and closing. In clothing, bags, shoes and other products, zippers are commonly used to replace traditional closure methods such as buttons. The role of zippers is mainly reflected in the following aspects：

1.  Easy to use: zippers are easier to open and close than traditional buttons, and they are more convenient and fast to use. 

2.  Safety protection: Zippers can effectively close items to avoid falling or loss of items, increasing the safety of items. 

3.  Aesthetic effect: Zippers can make the opening part of the item more neat and flat, and enhance the aesthetics of the item. 

4.  Adjust the size: The zipper can adjust the width of the opening and closing as needed to facilitate the adaptation of items of different sizes. 

 In general, the role of zippers is to simply and conveniently connect two pieces of fabric together, and to ensure that the connection is firm and convenient.