Content Delivery Networks (CDNs) include multiple web servers in geo-proximity to major media markets for the caching of copies of website files for faster download speeds & file transfers. Most CDN companies require a transfer of DNS settings to the service provider so that the cached website files can be distributed over multiple international data centers. Some CDN companies also include anti-DDoS protection in the service. CDN caching of web pages can improve pageload download speeds to ~400ms.
Ease of use or integration with an existing web presence is a major factor to consider in selecting a CDN. Many services are as simple as "one click" to enable and most of the major/minor web hosting companies offer CDN plans. Price is another major factor to consider, whether the CDN integration is offered for free with a hosting account or if it is charged by the GB/TB of data throughput & the storage required on the remote servers. Uptime is another major factor, as well as network traffic, to consider when evaluating CDNs, including how they rank with Google Pagespeed tests for anonymous users.