APR, or Annual Percentage Rate, is the interest you'll have to pay back to the lender over the original principle borrowed on a credit card. APR determines the overall cost of the deal you make with an issuer. Thus, when looking for a credit card, it makes sense to find the lowest APR available at the moment.
There are several types of APRs applied - purchase APR, balance transfer and cash advances APR, as well as default APR. As a rule, some of the best interest rates (meaning the lowest rates) are available on excellent and good credit cards which require high scores and long credit history to qualify for. However, one can find some really enticing offers in the "less than good credit" consumer segment.
For customers whose credit ranges from excellent to good, the lowest APR on purchases and balance transfers credit card is Blue from American Express. Its extended 0% introductory APR allows saving on everyday purchases for as long as 15 months!
For an applicant with an average (limited) credit rating, meaning that he is building credit and has no bad payment records yet, the best-selling product is Capital One Platinum, a truly low APR credit card on purchases and balance transfers. Mind it though, this card does charge a moderate annual fee.
Those who do not qualify for these two cards due to bad credit history damaged by late and missed payments usually search for Centennial Gold MasterCard®/Visa from First PREMIER Bank. Though charging an annual and set up fees, it offers some of the lowest APRs in the segment of sub-prime credit.
All these credit cards are low interest as long as you pay on time. A single late payment may push you APR to the skies, which is called default APR.
If you were searching for a credit card, these three would give you the most favorable rates for your particular credit level.