Just to add to what _auroraborealis_ posted above: The cards are known as "YKTTW", Your Key To The World.
In addition to be a room access card, your card can do everything just like a Magicband, access your ticket entitlements, FP+, etc.. except be accessed by the long range RFID readers on some rides that have enhanced guest interaction or Attraction Photos.
To claim your Attraction Photo, you will have to stop by the video unit showing your picture and "Touch" YKTTW card to the sensor. In a FP+ line just touch your card to the Mickey Head for access, also at the Park front gate touch points, and finally at Point of Sale locations for Room charging if you have that enabled.
Note: you can also just use it to access your room.
Dave