Decreases the force of a collision
Nothing until they're activated. Then sodium azide is reacted to rapidly produce nitrogen gas, which inflates the bag.
The light come on when the system detects a problem and sets a trouble code. You should have it diagnosed by a trained technician. The airbag system is not for do it yourselfers.
Both, to have effective communication you need to be a good communicator but you also need to listen to what the other person has to say.