In computing, PC Card (originally PCMCIA, or PCMCIA Card) is the form factor of a peripheral interface designed for laptop computers.
The PC Card standard (as well as its successor ExpressCard) were defined and developed by a group of industry-leading companies called the Personal Computer Memory Card International Association (PCMCIA). The United States computer industry created the Personal Computer Memory Card International Association to challenge the Japanese JEIDA memory card devices by offering a competing standard for memory-expansion cards.
In 1991 the two standards merged as JEIDA 4.1 or PCMCIA 2.0 (PC Card).
PC Card was originally designed for computer memory expansion, but the existence of a usable general standard for notebook peripherals led to many kinds of devices being made available in this form.
Typical devices included network cards, modems, and hard disks.
The cards were also used in early digital SLR cameras, such as the Kodak DCS 300 series.
The original use, as memory expansion, is no longer common.
Many notebooks in the 1990s came with two type-II slots with no barrier in between (allowing installation of two type-II cards or one, double-sized, type-III card). With the removal of legacy ports, most contemporary notebooks only feature a single type-II card slot
Source: Wikipedia (http://en.wikipedia.org/wiki/PC_card)