Credit card help, what's a APR?

Kind of naive but I don't really understand what a APR is when dealing with credit cards or any type of loan.

I know the stands for Annual Percentage Rate. What I don't understand is percentage of what? I know annual means yearly, right?

So is this(APR) a fee that I'm paying yearly? I'm so confused can someone please explain? Thank you
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It isn't a fee. It's a cost of borrowing money. If you don't borrow money, or don't carry a balance from month to month then you don't pay it. Some cards do have an annual fee where even if you don't use the card at all you have to pay the bank money to keep your account. What it means is if you carried the same balance for a year that's how much more you'd owe in percent after that time. So an APR of 10 % on $5000 means you'd pay $500 in interest. The interest due each month is derived from the APR. So if your APR is 12 % each month your interest is 1 percent. The $5000 in our example would be $50 in interest.
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The APR is the maximum interest allowed by law that any lending institution can charge for the use of it's money .. It can run as high as the usury laws of your state allows .. Usually capped at 29.99% .. Most banks and credit cards APR is 14 to 18 % but can be 21% for department store revolving accounts or for poor credit scores..These can also be based on income to loan ratios..
Yes it is the fee you pay for the use of the money borrowed..