Ignition Cable: Description and Operation

Distributor Cap And Spark Plug Wires W/Resistor Type Plug Connectors:

The ignition wires serve as electrical conduits to conduct the sparking energy from the ignition coil to the distributor center electrode and then from the distributor cap terminals to the individual spark plugs.
Most modern ignition wires are static suppressor wires and are constructed of a carbon impregnated, multi-filament synthetic fiber core surrounded by layers of a heat resistant silicone rubber insulation. The high resistance of these type of wires (usually about 7K-9K ohms per foot of wire) helps reduce radio static interference from the ignition system. This also reduces the possibility of induced voltages in the engine electrical harness that might cause false signals in sensor circuits.
Some Audi models use low resistance wires with auxiliary resistors built into the connectors on the wire ends. These auxiliary resistors provide the same radio static suppression as resistor wires while reducing the possibility of ignition wire failure due to excessive resistance (arcing through the wire insulation).