A cordless drill driver is operated using the speed control trigger. Squeezing the trigger starts the chuck turning.
The further you pull the trigger in, the faster the tool will go, but the less torque it will deliver.
The more you release the trigger, the slower the drill driver will go, but the more torque it will deliver. This is because the motor’s power is a combination of torque and speed, so the two have an inverse relationship (meaning that when one increases, the other decreases and vice versa).
Releasing the trigger completely stops the drill driver.