A content delivery network (CDN) refers to a geographically distributed group of servers which work together to deliver web content to users more efficiently. By replicating website content and storing it on multiple servers, CDNs can reduce the distance between the website's server and the user's browser, leading to faster load times and a better user experience. This is particularly important for websites that receive high traffic, as CDNs can distribute the load across multiple servers to prevent overload and improve overall website performance.