I had a 2003 Accord Euro R with same card
It is called Smart Card. When you have this card in your pocket, you dont need the key to open the door locks or start the car
All you have to do is simply keep it in your hand, go to driver side door and feel a button on the front door knob...press it ....lights will blink in your smart card and car will open....then once inside simply turn the ignition and car can be started.....
Cars with smart card have sort of extended ignition key hole so that it can be turned by hand
Thats what it is ...hope it helps