Sometimes called "original routing", "node routing", or "port linking", this is a way of configuring repeaters to connect to each other 1:1 without the need for a reflector. It is the repeater level equivalent of callsign routing, but instead of linking one user to another, it allows a user to be heard by all users of a repeater. Users need to use callsign routing or to zone routing to respond, so it's important to mention what node and repeater you are using as your gateway so that others can configure their radios to respond.
To make it easier for users of the remote repeater to respond one might to use repeater linking which would only require users to be using the usual gateway CQ configuration to respond.