A network layer model term.
A network layer model is an abstract way to catergorise the various operations needed within a network. For example there is the 'four layer internet model', there is the TCP/IP suite and the more complicated 'OSI network model'.
The application layer is one of the layers within those models.
The application layer groups together those applications whose purpose is to support the communication protocols within the network and also support the interface methods used by each host within the network.