Carnet de Passage
A Carnet de Passage is a customs document that identifies a vehicle - it's easy to think of it just like a passport for your vehicle. It is absolutely mandatory to enter some countries with a vehicle.
Definition
The Canadian Automobile Association explains a Carnet de Passage as follows:
The Carnet can be thought of as a passport for your car. It offers a guarantee to a foreign government that the vehicle identified in the Carnet, if granted temporary importation status, will be removed from the country within the time limit imposed by the respective jurisdiction. In the event that the vehicle is not removed within the imposed timeframe, the country may claim from the issuing association all duties and taxes that would be required to permanently import the vehicle to that country. Using the Carnet is an alternative to leaving a cash security deposit with a foreign government. It allows free movement and unencumbered access between foreign countries....