Common Terminology in System design

CDN:
Content Delivery Network or CDN is a system of servers which are geographically distributed to server static content like images, videos, etc to the users across the globe.

The servers in CDN are called as edge servers.

Important points to keep in mind:
Geographical distribution: The CDN server(edge servers) are geographically distributed, this means when a user requests a content, it can be served from the nearest edge server resulting in low latency.
Caching: The contents are cached on the server, when the same content is requested again, it is served from the cache resulting in quick response time.
Load balancing: CDNs use load balancing to distribute the load across the different servers to prevent a single server being overwhelmed with most of the request, insuring reliability and availability.
Dynamic routing: CDNs can dynamically route the request to best performing server based on real time conditions like server load and network latency.

Example: Imagine a global e-commerce application having its origin servers in US but its edge servers (CDN system) are located across the globe, hence if a request comes form India, it will be served from the nearest edge server instead of going all way to origin server which is US. This will improve response time of application resulting in better user engagement.