Inside the key to the car there is a built in “Trandsponder”. This constantly send out a code signal into the air. When this code signal, no doubt its encrypted is picked up by the correct car, this car reacts with a handshake of the car and the Transponderkey. This handshake results in either an approval or a rejection of the key.
If you are approved and you want to enter your car you just approach it and press the button on the door handle, the car will be unlocked and you will be let in to the car.
You take place behind the wheel and apply a foot on the brake then you press the button on top of the gearshiftselector or at the old keyhole..
Wham the car which has already approved you as the correct driver (thanks to the key) puts on the ignition on and start the engine.