For those with traditional internal-combustion engines in their cars, there's no such thing as "one-pedal" driving. For those with experience driving a plug-in hybrid or purely battery-electric car, it's a unique benefit.
To explain what exactly one-pedal driving is, Jason Fenske of Engineering Explained is here with an episode dedicated to the function. In the video, Fenske drives a Nissan Leaf to show how the system functions. It's not exclusive to the Leaf, though. Teslas, the Chevrolet Bolt EV, and plug-in hybrids like the now-dead Chevrolet Volt house the capability to some extent.
Basically, one-pedal driving is exactly what it sounds like. The driver doesn't need to touch the brakes to bring the car to a stop. In an electric car, or a car with an electric motor, the powertrain requests electricity for the motor to propel the car forward and accelerate. However, when stopping, it can do the opposite. The car uses its kinetic energy, turns that into electricity, and slows down in the process. All the while, it dumps those recovered electrons back into the battery. This is called regenerative braking.
At the same time, this process lets the car come to a complete stop with help from the hydraulic brakes. In the Nissan Leaf's case, the car can come to a complete stop in its "e-Pedal" mode. When the car stops totally, it engages the hydraulic brakes to hold it in place. This isn't the case, however, with the Chevrolet Volt extended-range electric car, for example. The driver will need to leave their foot on the brake pedal to come to a stop, which doesn't give it true one-pedal driving capability.
Should the driver need to make an emergency stop, the brake pedal works just like normal and will lock up the hydraulic brakes to come to a stop as needed. Also good to know: the brake lights still function when using one-pedal driving to let drivers behind the car know the vehicle is slowing down.
Dive into the world of one-pedal driving in the video above.