PCI-DSS stands for Payment Card Industry Data Security Standard.  This is a technical and broad-ranging set of security requirements created by the Payment Card Industry, laying out what Merchants need to do to protect customer information.  The PCI Council requires that Merchants meet this set of security requirements if their business accepts, transmits or processes customer payment cards, such as credit cards or debit cards.  Merchants that do not comply with these requirements can be penalized in a number of ways, up to and including having their card-processing privileges revoked, leaving them unable to accept customer payment cards.