Content Delivery Network (CDN)

A content delivery network (CDN) is a network of servers spread around the world that store copies of your site's static files, such as images, stylesheets, and scripts, and serve them from whichever location is nearest the visitor. Instead of every request traveling back to your main web server, the file comes from a nearby node.

Distance matters online: a visitor in Tokyo loading files from a server in Virginia waits longer than one nearby. A CDN shortens that trip, which speeds up delivery and takes load off your origin server. It is closely related to caching, since the network holds onto copies rather than fetching them fresh each time.