The Fluid Router is a machine added by Immersive Engineering. Unlike most machines, it does not consume any energy. The Fluid Router is used to organize and distribute fluids.
The Fluid Router has a GUI. It has a collection of slots for each side of the Fluid Router. Clicking a liquid container (like a Bucket) into one of these slots will not put the fluid into the slot, but it will configure the Fluid Router to output that fluid through that specific side into a tank when it enters the Fluid Router. If the Fluid Router doesn't have configuration for a specific fluid, it will output that fluid through a random side. The Fluid Router will only output a fluid if it can output to a tank, and if it cannot route a fluid, that fluid will not be accepted into the Fluid Router. Lastly, fluids cannot be outputted from where they entered.
The Fluid Router be configured to filter based on NBT values inside the GUI on each side.