An Access Point Name (APN) is the name of a gateway between a mobile network and another computer network. A mobile device making a data connection must be configured with an APN to present to the carrier in order to have an active data connection. The carrier will then examine these settings to identify what type of network connection should be created E.G which security methods should be used between the two networks. In short an APN is the settings needed on a mobile device to receive and send data to the network (Usually the public internet).
For your Country's APN Settings please see the below links: