Answer: borrowing.
When you have money you have to decide whether you want to spend/invest it or save for future spending. If you save it is because you can earn interests and increase the value of your money.
Yet, you have a third option to consider. You can borrow money. Whether it is better to borrow money to spend today is a financial issue, and the convenience will depend on the cost of that money (the interests that you have to pay to the bank) and the benefits of using it.
