When you borrow money, you trade the convenience of having the money now for more money in the future. The extra money you pay is called interest. Borrowing money is something that should require a great deal of thought because it requires you to make commitments in the future for a time where you can't accurately predict you financial situation.
In general you should avoid borrowing money for items that decrease in value. Borrowing money to pay for something that has a reasonable chance of increasing in value is a bit wiser, but still should be done very carefully.