Heel and Toe
Heel and Toe (or "Heeltoeing") is a technique essential to master in racing. It involves both slowing down the car and revving up the engine at the same time as you approach a corner.
When you approach a corner, you need to begin threshold braking to slow the car down to the speed you want. The stress in on smooth but quick and powerfull braking into the turn-in. However, such a significant slow down would require a downshift in gears. The problem being that, when shifting down (as opposite to shifting up), the engine revs tend to drop too low, creating engine drag (amount of revs that don't match) that puts load on the driven wheels and on the gearbox. To ensure smoothness and the ability to maximize traction by not inducing wheelspin due to excessive drag, heel and-toe is brought into use.
The application is for the driver to press the brakes with his right foot, while the left foot is still on the rest-pedal, gently squizzing it to increase feel while braking. Now, de-clutch with the left foot, choose the most appropriate gear (which is the one to get you quickly out of the corner). In the meanwhile, rotate the right foot so the ball of the foot stays firmly on the brakes, and the heel of the foot is touching the gas pedal. Now, gently blip the throttle with the heel as much as nessecary to rev up the engine as nessecary and re-engage the clutch. The left foot can now return to the rest pedal (squizzing it) or be used for left foot braking.
Custom racing pedals have extended acceleration pedals that enable a more comfortable heel and toe. In these cars, an easier technique is simply to use both sides of the foot for the gas and brakes.
Alternatively, if the pedal height is not equall, you might also use a similar technique: Use the ball of the right foot to brake, rotate your heel right, but use the right side of the foot's tip to blip the power, rather than the heel itself. This is called Tip & Toe (or "Tiptoeing") and is generally more accurate than Heel & Toe. Sometimes, the side of the foot right above the heel is the one used, rather than the heel itself (in proper Heel&Toe) or the tip of the foot (in Tip&Toe).