A PoP is a physical location where a network provider has installed equipment — routers, servers, transit connections — that other networks can peer with.
Explanation
Cloud regions, CDN edges, and ISP interconnect points are all PoPs in the general sense. When someone says "we have a PoP in Frankfurt", they mean their network has racks in a Frankfurt data centre where users' traffic terminates. More PoPs closer to users generally means lower latency, though the topology of the transit network in between matters more than the raw count of PoPs. Consumer VPN marketing that boasts "500 servers in 60 countries" is largely counting PoPs, which is a weaker signal than routing quality between them.
Related terms