At a minimum, the standards define the physical dimensions of the card and the geometry of the terminals which read those cards (for example, the slot in an ATM). Then, depending on the reading technology, the standards define how the card “couples” with the card terminal and thereby communicates with the underlying application (for example, motorized mag strip readers in ATMs, magnetic stripe swipe readers in Point-of-Sale terminals, slot readers in hotel card key locks).

Benefits
International acceptance of standard card schemes allows anyone to use a credit or debit card to pay for goods and services anywhere in the world; or to draw cash from automated teller machines (ATMs) in the local currency. Equally as important is denying access to applications and services to which the proffered card is not entitled.
Mass transit authorities around the globe issue smart cards that speed up access to the local metro/subway/tube/bus for our daily commutes.
One hundred countries around the world have issued about 350 million of the new ePassports.
Users
Virtually everyone is a potential user: the general public for payment cards, mass transit ticketing, access control.