Nowadays, in racing, is not enough with a regular, usual braking technique which you apply brakes before turn in point. Some drivers developed a new advanced technique like 30 or 40 years ago trying to improve their lap times.
Drivingfast makes a perfect approach to this technique:
“Once you have cornering down to a fine art, trail braking is a method of further improving your lap times. When performing this technique at speed, it’s important to remember that the majority of the braking should still be completed in a straight line. However to squeeze every last ounce of performance from your car, you can start to leave your braking point slightly later and continue to use the brakes in the corner prior to the apex. Before you turn in, progressively start to ease off the brakes until they are fully released at the apex ready for the acceleration phase. Some cars do not react well to trail braking, especially those prone to lift off oversteer – although there will be more grip available at the front wheels while trail braking, the rear will be more prone to break lose. Beware!”
It should be easier to understand with the string theory:
“Work on coordinating your brake release with turning input. Only release as much as you are willing to turn. Only turn as much as you are willing to release. The relationship between steering input and brake release (even throttle) needs to be directly proportional. I call this ‘string theory’ in that you imagine that there is a string tied to the bottom of the steering that is connected to your big toe. If you turn the wheel that string will pull your foot off the pedal and if you push your foot down on the pedal it will in turn straighten the steering wheel. When driving on a track at or near the limit of adhesion (how much grip your tires have), too much brake release results in oversteer, while not enough brake release can cause the front tires to understeer.”
As always, practice makes perfect.