Cable... flex... lead... wire... what do all these terms mean?
A lead should convey an electrical signal (or light in the case of fibre optics) with minimal degradation of the signal over the length of the lead and/or its connectors. To this end, different types of electrical signal require different lead designs, as the nature of the signal (level, bandwidth and input/output impedance) will dictate the attributes of the cable and connectors used.