Short for content delivery network or content distribution network, a CDN is a global network that caches static content such as images, CSS, and videos for a website around the world. CDN helps improve the load time of a website by loading the static content from the closest CDN server.
For example, if a website visitor was in India and the web server was in the United States, each request made by the visitor must travel from India to the United States. Although each request may only be a few hundred milliseconds, a site that makes dozens of different requests can increase a sites overall load time. However, if the website was utilizing a CDN, it could make requests to a server that is closest to the visitor instead of having to make all requests to the original server.
The picture above is an example of a user in India accessing a server in the United States and then getting the static content from a closer CDN.
Below is a listing of some of the companies who provide CDN solutions.