The manual aerial receives radio waves so that you can listen to the radio in your car.
Aerials are usually made of stainless steel, sometimes chrome, rubber or aluminum. Manual aerials can be retractable and non-retractable and have different mounts, including pillar mounted and roof mounted. The pillar mounted aerial is mounted on a pillar bracket, which fixes to the door pillar of your car, next to the windscreen. The roof mounted aerial is fixed to your car roof but can also be attached to the hood, with a screw.
The manual aerial is operated by hand and requires you to adjust it while outside. The manual aerial is connected to your car stereo by an aerial cable which houses the conductor needed to receive radio reception, and the manual aerial is basically an extension of the center conductor inside the aerial cable.
The manual non retractable aerial is thin and flexible but, being constantly exposed, it will erode over time due to weather damage and is more likely to be broken accidentally. With a retractable manual aerial, you can extend and retract the aerial fully by hand, which means it is less likely to be accidentally broken off and is less exposed to the weather and high speeds, but the collapsible, hollow metal rods that allow this telescopic action can break. The manual aerial, like most parts, will end up wearing out and need replacing. A manual aerial will usually work well for about 4-6 years before you need to think about buying a new one, but careful and regular cleaning to avoid damage from dirt will help this part to last longer.