Gift card churning, at it's basic definition, is buying a gift card at a discount using reseller sites or points you may have through a credit card or some other way of getting it cheaper and then turning that gift card into one you can use better or sell. Some retailers will allow you to buy a gift card with a gift card so some people just 'churn' once to get what they want. Others will 'churn' through multiple stores going through cash back sites each time to earn even more money.