What is "port forwarding"

n. (context computing Internet English) The forwarding of a network port from one device to another; ''especially'', such forwarding when done to provide an external user with access to a port on a private IP address.

In computer networking, port forwarding or port mapping is an application of network address translation (NAT) that redirects a communication request from one address and port number combination to another while the packets are traversing a network gateway, such as a router or firewall. This technique is most commonly used to make services on a host residing on a protected or masqueraded (internal) network available to hosts on the opposite side of the gateway (external network), by remapping the destination IP address and port number of the communication to an internal host.