Your vehicle is how you travel to the different areas in Dead Frontier 2. They act as a fast travel and require Fuel to use. Areas further away will require more Fuel to go to, as well as having higher requirements for thirst and hunger for your character to travel. After you've traveled the vehicles Fuel is consumed and your character loses a little Food and Water. Traveling happens instantly, there is no waiting or timers.
You can upgrade your vehicle with different parts. These affect things like how much Fuel your vehicle can store, how many items you can store in vehicle's storage, and how efficient the vehicle is on gas.