CDNs are essential in modern web development for improving performance, user experience, and security. They use geographically distributed edge servers to cache and deliver content efficiently. Key benefits include faster page load times, better scalability during traffic spikes, enhanced security against DDoS attacks, reduced bandwidth costs, and improved SEO. Common use cases include static content delivery, media streaming, e-commerce, and global websites. Major providers like Cloudflare, Akamai, Amazon CloudFront, Fastly, and BunnyCDN offer diverse features. Best practices involve selecting a suitable provider, optimizing caching, enabling compression, and securing configurations. Emerging trends like edge computing and AI optimization are shaping the future of CDNs.