There are two major families of smart cards. The older one is the contact card (which has a small golden contact area near the edge of the card). The more recent one is the proximity smart card (also known as contactless smart cards). These credit-card-thin, ISO14443A compatible, technically mature cards are very similar to the thick, traditional proximity cards used in the access control industry. For a legitimate user doing only access control,
there seems to be no functional difference between the traditional proximity access control card and the modern proximity smart card.
To the security professional, however, there is a world of difference, including security, room for expansion, read-write capability and multi-application support.