Piggybacking credit is a strategy where someone with good credit adds another person as an authorized user to help improve their credit score. There are two types: traditional, involving family or friends, and for-profit, involving companies. This method has both advantages, such as improving credit scores and history, and disadvantages, like potential risks for both parties involved. It's most effective for those with thin credit files or low scores. Trust and understanding are crucial in piggybacking arrangements, and one should be cautious, especially with for-profit services.