Left foot braking is a pretty simple driving technique that you can use to help control front and all wheel drive cars through turns. It’s useful for a few reasons:

I would say the most important reason is to control the car’s balance. When you brake, the weight of the car shifts towards the front wheels. Purposely shifting the weight forward in a turn will give the front wheels some extra traction to dig the car out of the exit. Applying the brake against the throttle allows you to get the proper weight shift without over-braking and slowing the car too much.

The second reason that left foot braking is faster for front wheel drive cars is because it helps the differential. It’s easy for a car to lift its inside front wheel while trying to accelerate out of a turn. Reduced resistance on the lifted wheel will cause the differential to send more power to it which generally results in your engine power doing a one wheel burnout if you’re really trying to drive fast. Left foot braking prevents the lifted inside wheel from spinning too much so a higher percentage of the engine power goes to the outside front wheel to pull you out of the corner.

Chris Harris demonstrates the technique and talks about these benefits in this vintage AutoCar video: