CDN - Do you need a Content Delivery Network?
CDN's (Content Delivery Networks) help to distribute the load created when a website has lots of visitors. They work by storing copies of a websites files on multiple servers which are situated in different geopraphic locations. The principle is that a visitor from the UK would be served files from say a UK data centre while a visitor from the US visiting the same URL or webpage would recieve files from a US data centre meaning that each visitors browser displays the same content quicker because the files have less distance to travel across the internet.
Who Needs to use a CDN?
Anyone can use a CDN but sites with a high volume of visitors will benefit more. Many webhosts cram as many sites as possible on to a server, that means that using a wordpress site as an example there are thousands of databases, files and images all stored on the same server and all trying to use the same resources. One of the benefits of using a CDN would be that you could store all of the images for your website within a CDN and leave the core files and database on the original server.
The benefit of doing this is that if you had a typical sales or landing page with say 20 images and your site was heavily promoted and recieved 1000 visitors at the same time, your server would perform better if the images were in a CDN as your server would need only to process and deliver the core files and database calls (think basic framework) and the CDN would deliver the images for your page from other servers. The net result is that your server is using less resources and less bandwidth while the bigger image files are being delivered from a more local server to your visitor.
This results in quicker page load speeds for your visitor (which Google and other search engines also want to see) and less risk of heavy demand bringing down your server so that no-one can view your pages.