On the rear of credit cards and other bank cards there is what is known as a Magnetic Stripe. On this strip of magnetic tape can be stored information that a card reader will pick up and translate to whatever machine it is linked to, ie. cash register or PC. As a rule in the UK, there are three 'tracks' (lines of data) that can be stored on the strip, track 1, track 2, and track 3. Commonly, most card readers pick up track 2.
A substantial amount of information can be stored on the back of a card in coded form. For example a club members address, phone number and date of birth, or some password that is required for entry. If you require a card that needs data encoded and are unfamiliar with the details don't hesitate to call, we will be only too glad to help.