A CDN (Content Delivery Network) is a distributed network of servers that delivers content to users. Joomla sites often use a CDN for images, styles, scripts and other safely reusable resources.
How delivery works
The origin hosts the application and original content. A CDN node may fetch a resource from it and keep a copy according to caching rules. When a suitable copy is available, the node can respond without another origin request.
A CDN does not necessarily cache every response. Settings, headers, cookies, parameters and lifetime affect reuse. It does not replace hosting or make a failed application fully functional.
Joomla integration
For Joomla, decide which resources to cache and how their copies will be updated. Accounts, forms and dynamic operations need appropriate rules. Caching all HTML without considering users can expose personal data.
After connecting a CDN to Joomla, check HTTPS, resource links, fonts, login and forms. When files change, purge the relevant copies or version their URLs. Inspect both the origin and CDN response.
Conclusion
A CDN can reduce latency and origin load when delivery rules match the content. Reliable setup includes exclusions, invalidation and user journey checks.