It is a device that takes the place of the keycard issued by other lines. It has some additional functionality, but at a minimum unlocks your cabin door hands-free. In conjunction with the app, you can use it to find your traveling companions, order drinks and food to be brought to you almost anywhere on the ship, make purchases in port and earn 8% back, identify yourself to crew such as bartenders, servers and folks manning the gangways. For some, it just opens the cabin door. For some, it is a scary 1984 Big Brother device and they request keycards as if they provided a cloak of invisibility. It is a potential swallowing hazard for toddlers. It is a badge of honor to some, as it shows your CC status. It is a souvenir printed with the ships name and sailing date. All of this and more.