A "Magstripe," short for magnetic stripe, is a black strip found on the back of credit cards, debit cards, and some identification cards. It contains three tracks of data that store information about the cardholder, such as their account number and expiration date. When swiped through a card reader, the data is read and processed for transactions. Magstripes are widely used in payment systems and access control. They are a convenient way to make purchases or gain entry to secure areas. However, they are less secure than newer technologies like EMV chips and contactless payments, which offer better protection against fraud.