PoP

A point-of-presence (POP) is an artificial demarcation point or interface point between communications entities.

Telephone systems

In the USA, this term became important during the court-ordered breakup of the Bell Telephone system. A point of presence was a location where a long-distance carrier could terminate services and provide connections into a local telephone network.

Internet

An Internet point of presence is an access point to the Internet. It is a physical location that houses servers, routers, ATM switches and digital/analog call aggregators. It may be either part of the facilities of a telecommunications provider that the Internet service provider (ISP) rents or a location separate from the telecommunications provider. ISPs typically have multiple POPs, sometimes numbering in the thousands. POPs are also located in Internet exchange points and colocation centres.