CDNs are vital for enhancing website performance by using geographically distributed edge servers to deliver content efficiently. They reduce latency, lower bandwidth costs, and improve security against DDoS attacks. Different CDN types include traditional, dynamic, P2P, and private. Choosing a CDN depends on coverage, speed, security, pricing, and integration. Popular providers include Cloudflare, Akamai, and Amazon CloudFront. Optimization techniques include cache control, compression, HTTP/2-3, image lazy loading, and edge computing. Advanced strategies involve using multiple CDNs, smart routing, and real-time analytics. Challenges like cache invalidation and SSL errors can be addressed with proper configuration. Future trends include Edge AI, WebAssembly, and 5G/IoT optimization.