Jet Pump

The jet pump utilizes the velocity of fuel returning from the engine to produce vacuum in it.
Using the pumping effect produced by the vacuum, the jet pump transfers fuel from the sub-compartment and main compartment of the fuel tank to the fuel pump.
When the return line nozzle is clogged, the fuel sent back through the return line flows back into the fuel tank via the relief valve.

Fig 1: Identifying Jet Pump Relief Valve, Return Line And Nozzle
Courtesy of SUBARU OF AMERICA, INC.