A point of presence is a place the network can answer from. In a CDN it is where TLS terminates, cache lives and — on a miss — the origin is pulled. More PoPs only help if they are actually on the path your users take.
PoP versus a single data centre
A data centre you rent is where the origin runs. A PoP is where the copy runs. Users should meet the PoP; the PoP should meet the origin only when it must.
Aptranet Cloud CDN and Cloud DNS share 210+ points of presence across six continents. The DNS question and the HTTP response can both be answered close to the resolver and the browser.
Peering is why the map is not a sticker
A PoP that is poorly peered is a nearby building with a long driveway. 14,000+ peering partners and 120+ IXPs are how requests get into those buildings without bouncing through extra transit.
When you compare vendors, ask about peering and IXPs, not only city pins.
Capacity is the other axis
Live streams, game launches and software releases care about terabits, not only milliseconds. Cloud CDN is built on 200+ Tbps of capacity with large-file optimisation for those objects.
A small cache in many cities still overflows if the object is a 40 GB depot and the launch is global.
DNS PoPs and CDN PoPs
Authoritative Cloud DNS uses 210+ Anycast servers. That is a PoP job for packets that never become HTTP. A website that is fast in HTTP but slow to resolve still feels slow.
Put the zone and the distribution on the same footprint when you can.