When using a brushed motor in your car, if you let off the throttle, the motor itself will exert some force to slow itself (and the car) down. Because of this, some ESC's offer a setting for push control (aka anti-drag, or coast), which will attempt to supply just enough power to the motor to overcome the motor's natural drag, so it can coast more freely.
The value of anti-drag determines for how long the effect will take place after you release the throttle. Higher values means the ESC will counter the motor's natural braking for longer.
See our article on electronic speed controller for more info on ESC settings.