Content Delivery Network (CDN) is a network of servers distributed globally, which deliver web pages and content to users based on their location. CDNs reduce the delay (latency) caused by the physical distance between users and web servers. CDN is necessary for large websites with global reach, which have a high volume of traffic and content.
The goal of setting up such a network of proxy servers and data centers is to provide users with an always available website with high performance. Many industry leaders take advantage of content delivery networks, e.g., e-commerce stores, online streaming services and downloadable content providers (softwares, applications, and media).
The data centers, generally referred to as points-of-presence, store cached content. Each point-of-presence can have multiple servers caching the website content, and each server is responsible for delivering data to users who are in its proximity.
For example, the image below shows how a request to load www.acme.com is handled. Acme.com points to Akamai CDN server to load the image on the requested web page and loads rest of the page information itself. Even if the server capability of Acme.com is reserved, the web page will load faster using Akamai server.