It simply allows you to share your signals: One output to several inputs.
It’s passive. You don’t need to power it. It won’t draw any current.
It’s Ultra Low Noise and its THD approaches 0%.
(Yeah, it’s a cable. And, well, honestly, any piece of wire can pick some noise and can act either as a capacitor or as an inductance.)
In Passive Multiple, one input is directly connected to 3 outputs. Actually, any jack can act as an input or as an output. It’s important to connect only one module output to the Passive Multiple input, or it could damage the weakest module’s output.
It’s possible to daisy chain several Passive Multiple. If jack n°1 is unconnected, the input signal can be delivered by a “master” Passive Multiple.
Pluging a jack in connector J1 disconnect the “slave” input and let your Passive Multiple standalone.