Yes, for the record, 12-volt DC plugs are for use in your vehicle. But, this question gets asked quite a lot and deserves a closer look. Considering it typically will not take too long to inflate the equipment that needs air, it is probably advisable to leave your car on.
While you could leave your car off, there is no telling how long it would then take to inflate your equipment. Do not worry about draining your car battery too much, though, as that will not be an issue unless you leave the pump on for an extended period.