You summoned spirit that that assumes the form of a vehicle of your choice. The vehicle has the statistics of a normal vehicle of its sort, although it is celestial, fey or fiendish  (your choice) in origin.

Note that the spell does not summon an animal to pull the vehicle unless cast at a higher level.

While driving the vehicle, you are considered proficient with vehicles of its type. You add double your proficiency bonus to ability checks related to driving it. Spells that target yourself can also target your vehicle.

When the vehicle drops to 0 hit points, it disappears. You can't have more than one vehicle bonded by this spell at a time. As an action, you can release the vehicle from its bond at any time, causing it to disappear.

At Higher Levels: When you cast this spell using a 3rd or 4th level slot,  the vehicle appears with a team horses (celestial, fiendish or fey) to pull the vehicle. The horses will not fight and will instantly return to their plane of existence if attacked. Or you can conjure a boat large enough to carry six medium creatures. 

If you use a 5th or 6th level slot, you can conjure a sailing ship, or a dirigible / submersible large enough to carry ten medium creatures.

If you use 7th level or higher, you can conjure any type of vehicle.

(Modified from dnd5e wikia dot com's homebrew spell for the modern setting "Summon vehicle")