The main purpose of using a Content Delivery Network (CDN) is to enhance website performance and availability by distributing content across multiple geographically dispersed servers. This reduces the load on the origin server and ensures that users can access content from a server closer to their location, resulting in faster loading times and reduced latency. CDNs also improve website resilience by providing redundancy and mitigating traffic spikes or server failures. Additionally, they can enhance security through features like DDoS protection, making them essential for businesses aiming to provide an optimal online experience for users.