APR Explained
The APR rate (Annual Percentage Rate) of a credit card is very important because it helps you compare the repayment cost of credit cards against one another. Usually, the higher the APR on a credit card, the more you'll have to repay on any sum of money you have borrowed (assuming that all other things are equal) e.g. a credit card with an APR of 13.9% is going to cost you more than one with an APR of 9.9% over the same period of time.
The APR does not include all the costs of a credit card, for example, late fees or over limit fees, but it tells you about the most important one. If you are looking around for a new credit card you usually want a card with the lowest APR rate possible.
This is only one factor to take into account though. A credit card may have a low APR but if carries a service fee, late payment penalties or high cash withdrawl fees then this may effect how much you are being charged overall.