An Access Point Name (APN) is the name of a gateway between a GSM, GPRS, 3G or 4G mobile network and another computer network, frequently the public Internet.
A mobile device making a data connection must be configured with an APN to present to the carrier. The carrier will then examine this identifier to determine what type of network connection should be created, for example: which IP addresses should be assigned to the wireless device, which security methods should be used, and how or if, it should be connected to some private customer network.
More specifically, the APN identifies the packet data network (PDN) that a mobile data user wants to communicate with. In addition to identifying a PDN, an APN may also be used to define the type of service, (e.g. connection to Wireless Application Protocol (WAP) server, Multimedia Messaging Service (MMS)) that is provided by the PDN. APN is used in 3GPP data access networks, e.g. General Packet Radio Service (GPRS), evolved packet core (EPC).