The Fuel Tank Vent is connected to the Fuel Vent Tube.
The purpose of the vent tube is to allow air in to the fuel tank so that a vacuum is not created when the fuel is being fed through the fuel line.
Most of the time the Vent line is connected to a fuel line grommet that is installed on the fuel tank.
The fuel return line and the fuel line are also connected to the fuel line grommet.
The other way a fuel tank is vented in other engines is by use of a fuel cap with a air vent built into it.