CDN: definition
A CDN, or content delivery network, is a set of geographically distributed servers that serve a site's static files from the point closest to the visitor.
What a CDN actually changes
Without a CDN, every visitor receives a shop's images, stylesheets and scripts from a single server, often located in one particular country. A distant visitor faces a longer network round trip before their browser even starts displaying the page. A CDN copies these static files onto servers spread across the world, and routes each visitor to the copy closest to them.
For a PrestaShop or WooCommerce shop, the effect shows up mainly on product images and the theme's CSS and JavaScript files. These files rarely change, which makes them ideal to distribute via a CDN, unlike dynamically generated pages (cart, customer account) which stay served by the origin server.
A CDN doesn't replace decent hosting or a well-tuned application cache: it reduces the transport latency of static files, without speeding up the calculations done server-side.
Frequently asked questions
Is a CDN useful for a shop that only sells in one country?
Does the CDN affect SEO?
Does PrestaShop or WooCommerce need a specific CDN?
Describe your need in one minute
A few targeted questions so I can reply with an estimate rather than another questionnaire.