The port monitor is responsible for transmitting data to the printer as well as checking status of the printer.
A port monitor is required to support a minimum set of functions in order to function properly.
Windows has 2 port monitors that are included: The local port monitor, and the TCP/IP port monitor.
The local port monitor has no configuration options, and can send data to parallel ports, serial ports, network shares, as well as the FILE: port.
The TCP/IP port monitor is configurable and can send to network printers that support LPR or RAW protocol.
There is nothing stopping a port monitor from being a language monitor also. As a matter of fact a port monitor may also report itself as being a language monitor, and the same minimum set of functions is required for both types of monitors.
Virtual Port Monitor works as a Port Monitor.