Brake pads wear down over time due to friction and heat generated during braking. The process of brake pad wear involves several key factors:

1. Friction: When you press the brake pedal, the brake pads clamp down on the rotors (or discs). This clamping action generates friction, which slows the vehicle. Over time, the friction material on the brake pads wears away, reducing their effectiveness.

2. Heat: Braking generates heat, and excessive heat can cause the brake pad material to degrade faster. This is particularly true in situations where the brakes are used heavily, such as in mountainous driving or during emergency stops.

3. Debris: Road debris and contaminants can also contribute to brake pad wear. Small stones and dirt can get caught between the brake pads and rotors, causing abrasion and accelerated wear.

4. Rotor Condition: The condition of the rotors can affect brake pad wear. Warped or damaged rotors can cause uneven wear on the pads, leading to premature replacement.