A Content Delivery System (CDN) is a system put in place to try and improve a user’s ability to access the site. This process allows the user to access the site quickly and efficiently no matter where in the world they are.
Every website is hosted by a server in a certain location. If my website server was in the UK and I had someone try and access that server in Australia, there may be a delay due to the distance. The CDN system means that the website is not only on that origin server.
All servers in a CDN system have a little bit of every site. This means that when someone tries to access your site from across the world it does not need to connect with the origin server. It only has to connect to the nearest server to them in the system. A CDN system allows you to keep your websites having a fast load time and make sure it works efficiently across the world.