The **braking distance** is the space a vehicle travels from the moment the **brake pedal is pressed** until the vehicle comes to a complete stop. This definition is key to understanding why the correct answer is the first option.

- The braking distance is only a part of the **stopping distance**, which includes both the reaction distance and the braking distance. The reaction distance is the space the vehicle travels from the moment the driver perceives a hazard until they begin to brake.

- Factors such as **speed**, **vehicle load**, **technical conditions** (such as the state of the brakes and tires), **weather**, and **road conditions** can affect the braking distance. For example, a vehicle that is going faster or is on a wet surface will need more space to stop.

Therefore, the braking distance specifically refers to the stretch from when the brake is applied until the vehicle stops, which matches the first answer.