Usually found in NASCAR racing a coil bind setup has very soft springs at the front with stiff sprints in the rear of the car. This controls the pitch or rake of the chassis allowing the car to run with the front splitter close to the ground, maximizing down force.
This setup substitutes aero down force for mechanical grip that would come from stiffer front springs and tires.
The speed generated at the end of the straight pushes the nose of the car down to the coil binds to almost solid and the car is riding on the bump stops. This keep the nose of the car and the splitter low, creating aero down force and grip through the corner.
While coil binding results in faster lap times, it makes the cars more sensitive to dirty air coming off cars in front. This is seen where the cars in clean air tend to be a lot faster than those closing.