Final answer:
Fenders, also known as wheel arches, are the guards mounted behind the wheel that turn with it to protect against road debris.
Step-by-step explanation:
The guards which mount behind the wheel and turn with it are commonly referred to as fenders or wheel arches. These components are designed to prevent road debris such as mud, rocks, and water from being thrown into the air by the rotating tire. Fenders are an important feature on vehicles as they not only protect the vehicle and its passengers, but also pedestrians and other vehicles from debris. Additionally, they are sometimes integrated with the vehicle's design to improve aerodynamic performance and enhance its aesthetic appeal.