A content delivery network (CDN) is a distributed network of servers that can efficiently deliver web content to users. CDNs store cached content on edge servers that are close to end users to minimize latency.

CDNs are typically used to deliver static content such as images, style sheets, documents, client-side scripts, and HTML pages. The major advantages of using a CDN are lower latency and faster delivery of content to users, regardless of their geographical location in relation to the datacenter where the application is hosted. CDNs can also help to reduce load on a web application, because the application does not have to service requests for the content that is hosted in the CDN.

https://learn.microsoft.com/en-us/azure/architecture/best-practices/cdn