What is a CDN?

A content delivery network or content distribution network (CDN) consists of a series of  linked servers containing copies of data.  These server are contected to the internet at various places around the globe so as to maximize bandwidth for client computers downloading the content.  A client accesses a copy of the data near to the client, as opposed to all clients accessing the same central server, so as to reduce usage on that server.  CDNs also reduce bandwidth costs for the site owner.

Content types placed on a CDN usually include web objects (html, images), downloadable objects (media files, software, documents) and real time media streams.