Passive

Means no active (i.e. connected to a power supply) electronics are involved – such as sending a signal straight through a potentiometer control, instead of using op amps and other electronics to create a mixer circuit around it. Passive is cheap and easy, and does not add noise to a signal. But passive electronics cannot buffer one signal from another (meaning they might interact in undesirable ways), and cannot boost, offset, or invert a signal.