The aerial cable is an insulated cable containing conductors, that connects the car radio to the aerial via an aerial plug and aerial socket.
Leading from the radio inside the car, the aerial cable connects to the aerial on the outside of the car. The aerial cable has a thin central conductor wire inside which is protected by a metal braid, both enclosed in a plastic covering. The conductor wire is what carries the signal and enables you to receive radio reception.
The aerial cable can suffer from corrosion and this can cause a break in the cable. It is not unusual for the thin, fragile center conductor inside the aerial cable to break. If you have a faulty or broken aerial cable, the radio signal in your car will at best be intermittent and poor, or you will not be able to pick up a signal at all. More often than not a reception problem is caused by a faulty aerial cable.
If you need to replace your aerial cable this is a fairly simple and quick procedure to get right, provided you ensure you purchase a good quality replacement that is suitable for the make and model of your vehicle.