Content delivery networks (CDNs) enhance web performance by distributing content across a network of geographically diverse servers. This distribution minimizes latency by providing users with data from the nearest server, thus speeding up load times and improving site responsiveness. CDNs also optimize content delivery by using techniques like caching and load balancing, which enhance the user experience and reduce server load. Additionally, they can improve website security by providing DDoS protection and regular backups. Overall, CDNs are vital in creating efficient, secure online experiences.