A balance transfer is when you move existing debt from a high-interest account to a lower-interest one. The most common example: transferring a $5,000 credit card balance at 22% APR to a new card offering 0% APR for 12-18 months.
The math is compelling: that $5,000 at 22% costs about $1,100 in interest per year. Transfer it to a 0% card and pay it off in 12 months — you save the entire $1,100. Most cards charge a balance transfer fee of 3-5% ($150-250 in this case), but you still come out way ahead.
The catch: the 0% rate is temporary (usually 12-21 months). After the introductory period, the rate jumps to 15-25%. If you have not paid off the balance by then, you are back where you started — or worse. Smart borrowers use balance transfers as a tool to aggressively pay down debt, not as a permanent solution.