Read about electrical conductivity. That's really part 1. When you have something electrically conductive you can apply electricity to it and have it travel the full length of the cable. Think of it as a power cord or power lines. Power is constantly going through the line, you plug a cable in then plug it into a power supply. It then feeds that power to your PC. That is for the most part a steady form of power.
So USB, HDMI, any digital cable takes this philosophy but instead changes the power very slightly. Think of it as Morse code. There is a standardized header and footer for packets (can be anything but lets say 1v-1.1v-1v that tells the device at the other end that the next 8-10-20 power settings (based at an agreed polling rate) is a packet of information. Then at the end they might have the inverse for footer, telling the other device that the packet is finished. The rest of the packet would be like 1.11-1.12-1.11-1.14-1.13-1.11. On an oscilloscope (a device that can give a visualization of power feed) it would look like a wavy line dropping up and down randomly. Both devices have instructions on how to interpret this information and they turn that into whatever data you are dealing with.
The better and new the tech, usually the quicker this is done. So instead of a millisecond between changes it might be measured in nanoseconds, or adding more connecting cables. Either one can give you more bandwidth (how much data you can move in a measured amount of time).
Overclocking is about running something out of spec to improve performance. On a CPU it might mean increasing that polling rate significantly. A USB cable or another cable its generally about a cable not being rated for a given spec but it still working. Since the wire count generally doesn't change (well it did from USB2-USB3-USB-C) its possible that a cable was manufactured to strict standards originally allowing it to work at the faster polling rate when new specs come out.
Now none of this should be taken as fact. Its a very light coverage of how the tech works and may not apply to any spec and the packet design and power settings were pulled from but buttocks and not actually the spec for anything. This is again just to tell you how it would work, not exactly how it works.
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