A CDN (Content Delivery Network) is a network of geographically dispersed servers known as nodes. Each CDN node caches the static content of a website such as the images, styles, scripts, etc. Because most of your users' loading time is spent fetching this content, it makes sense to serve up these "building blocks" of a website on as many nodes as possible, distributed throughout the world.
When a user requests your website, the node closest in proximity to the user will deliver the static content. This ensures that the shortest possible route for the data to travel is used, resulting in reduced latency and therefore providing the fastest user experience.
The number one reason for using a CDN is to improve your users' experience in terms of speed, because as we know - speed is king!
The number two reason, and this is especially relevant in New Zealand, is to reduce international bandwidth consumption. The nodes within the CDN only need to make one request for the files on the originating server before being able to serve up multiple copies to overseas users.
Ensuring a consistent experience for all your users is important. Your website may be hosted in a particular region, but the majority of its users maybe be coming from an entirely different region. For example, your website might seem blazingly fast for New Zealand users, but if a good chunk of your visitors originate from Europe, their speed will not be as fast as you experience.
We're big proponents of keeping things simple, so we recommend not enabling a CDN, unless you fit any of the following criteria: