An anti-theft device makes it more difficult for thieves to drive your car. They lock down the steering wheel, brakes, or tires and are difficult to remove without the key. A manual disabling, or active, car anti-theft device is simply one the driver must physically put in place/turn on to prevent the car from being driven. The oldest manual disabling feature is the steering wheel lock. That's a built-in anti-theft device to prevent thieves from hotwiring your car.
Passive devices automatically arm themselves when the vehicle is turned off, the ignition key removed, or a door is shut. Active devices require some independent physical action before they are set, such as pushing a button, or placing a “lock” over a vehicle component part.