Dry nitrous jets are an important part of any N20 system.  When properly used, this is where your energy flow comes from. It spray's from the nozzle, into the intake pipe, then travels into the manifold.  From there is sucked into the combustion chamber to create the proper energy.  

These nitrous jets come in alternative sizes.  The nitrous jets range in sizes from .014 all the way to .125.  The size of the jet matter a lot.  The bigger the jet the greater spray the greater the energy.  

• Using nitrous jets 36/32 you make about 55 HP
• Using nitrous jets 34/35 you make about 65 HP
• Using nitrous jets 32/38 you make about 75 HP
• Using nitrous jets 26/46 you make about 100 HP

Those are all the jet sizes for a 4 cylinder nitrous kit engine.    Precision-machined jets are used for adjusting nitrous. Special internal taper minimizes turbulence.   The jets are also tapered as well.  Tapered means a gradual decrease in thickness or width of an elongated object.  This allows a better and consistent flow, with funneling action.  Results in very consistent flow and power.  This is something you are going to want to have.  Having an inconsistent  amount of nitrous sprayed into the manifold is something that you don't want to happen.  Using state of the art equipment, jets are made to provide you with the smoothest flow possible.  

Sometimes jets are called nozzles.  There is no difference in the meaning, because they mean the same thing.  Using different types of nozzles is going to depend on your set up.  Tuners would know, that its not a good idea to put the biggest nozzle you have on a stock motor.  You would want to save that nozzle for a more built up motor.