You're coming hot. The corner is looming large out the front glass and you need to get this vehicle slowed down quickly. If you stomp on that brake pedal, you're likely to lock up the wheels and blow right through the corner. If you don't use enough brakes, you're also going through the corner. Both of these scenarios are what most would call "not good." So how do you make it safely through the turn? By braking hard and smooth and trail braking through the corner.
When you're starting out an any driving school, the basic method of getting around a given circuit involves braking in a straight line and then accelerating out of a corner on to the next one. As you get good at this practice, you'll find more speed, and that means your braking points will change. Eventually, you'll find a given corner can be taken far faster than you considered before, but it will require carrying a bit of braking into the corner. This is trail braking.
How do you trail brake? You still initiate hard and smooth braking in a straight line as you approach the corner. Instead of releasing the brake right away once the speed is under control for the turn, though, you slowly roll off it as you take the turn. At the apex of the turn you can then roll back on the power and complete the corner. You've just trail braked your way through a turn and added another driving skill to your arsenal.
Wyatt Knox from Team O'Neil Rally School is a trail brake enthusiast and he's here to demonstrate the skill in a Subaru WRX on gravel. Watch and then re-watch this video, and then start practicing. It could make you faster on a racetrack, and it could save your butt if you're going too fast on a canyon road.