What is the ID for cloud?

May I ask how do I get the ids? Example:

savedCar1.id

savedCar2.id

Cloud.Objects.show({
    classname: 'cars',
    ids: [ savedCar1.id, savedCar2.id ]
}, function (e) {
    if (e.success) {
        alert('Success:\n' +
            'Count: ' + e.cars.length);
        for (var i = 0; i < e.cars.length; i++) {
            var car = e.cars[i];
            alert('id: ' + cars.id + '\n' +
                'make: ' + car.make + '\n' +
                'color: ' + car.color + '\n' +
                'year: ' + car.year + '\n' +
                'created_at: ' + car.created_at);
        }
    } else {
        alert('Error:\n' +
            ((e.error && e.message) || JSON.stringify(e)));
    }
});