A Content Delivery Network is a globally distributed network of servers (called edge nodes or Points of Presence / PoPs) that cache and serve content to users based on their geographic location.

Key idea: Instead of all users hitting your one origin server in, say, Virginia — a user in Tokyo gets content from a Tokyo edge node, and a user in London gets it from a London edge node.

Without CDN: User (Tokyo) ──────────────────────────────► Origin Server (Virginia) [HIGH LATENCY]

With CDN: User (Tokyo) ──► Edge Node (Tokyo) [LOW LATENCY] ──(if miss)──► Origin (Virginia) User (London) ──► Edge Node (London) [LOW LATENCY] ──(if miss)──► Origin (Virginia)