The venturi is an improved version of the original siphon (conduit) that applies the principles of fluid dynamics to hydroponics, allowing water to flow more efficiently to the top of your 3Dponics system. The shorter pipe acts as the air intake (attaching to the air bubbler via rubber tubing); the longer pipe acts as the outlet (transporting water to the top of the system).
For optimal performance, the venturi should be placed vertically inside the reservoir, immersed in the nutrient solution.
Bonus: The venturi is smaller than the Conduit and therefore takes less time and material to print. If you have a dual outlet pump (e.g. HagenMarina 200), you can power two or more 3Dponics systems with one air pump.