A system of geographically distributed servers designed to accelerate the delivery of web pages and files by routing user requests to the server that’s in the best position to serve them.
CDN services try to improve the speed and availability of web pages and files. Speeds matters to marketers because of its impact on metrics like bounce rate and shopping cart abandonment, and thus profitability. There have been many studies showing how each extra second (or fraction of a second) can cause a percentage of web page visitors to give up and leave.
There are many types of CDN services, ranging from expensive enterprise solutions to more accessible options that can be configured from WordPress plugins. ROI calculations for CDN services can get complex for larger organizations, but at a basic level it requires knowing the cost of different serving methods, and the marginal profit gained from better performance.
see also: Digital Marketing Tools
Why You Need a CDN for your WordPress Blog?
WPBeginner (October 8, 2014)
10 Free CDN Services to Speed Up WordPress
WPExplorer (July 9, 2013)
7 Reasons NOT to use a Content Delivery Network
SitePoint (September 27, 2011)
7 Reasons to use a Content Delivery Network
SitePoint (September 22, 2011)
Why should I use Google’s CDN for jQuery?
Stack Overflow (February 1, 2010)
Best way to use Google’s hosted jQuery, but fall back to my hosted library on Google fail
Stack Overflow (July 18, 2009)
CDN Usage Statistics