What are Ignition Leads?

It is the method in which an electrical current (as high as 35 000 Volts) is linked between the energy source (Coil) and the igniter (Spark Plug) inside the combustion chamber of an engine.

[In the picture below] An exploded view of the distributor on the left and on the right an illustration of where the ignition leads and distributor are in comparison to a engine.