I'll pm you the link.
It all comes down to the old "slow in, fast out" saying, as well as a little bit of knowledge about racing lines. In reality, if your opponent is taking the turn perfectly, you will not be able to pass them, no matter what you do. However, by maintaining a bit of a gap on corner entry, you're giving yourself room to capitalize on any mistakes they might make.
I will keep using the last corner at Deep Forest to explain this example. With the DC5 we raced last week, it was possible to take that turn at 112 mph (maybe the aliens could take it faster, but that was my best). In order to do that, you had to brake early to get the car settled, and then carry a bit of throttle through the apex. You also had to hit the turn-in and apex pretty much spot on, otherwise you'd have to scrub off too much speed to avoid having an off.
Now, let's say that going into that turn, the car in front of you slips up and only carries 108 mph. If you're right on their bumper when this happens, you have only two options: Hit them, or sacrifice your momentum by leaving the ideal line or braking. However, if you maintained enough of a gap in the braking zone, you should be able to carry your extra momentum through the apex and complete the pass on the front-stretch (or at least set up a clean pass into turn one).
Make sense?