Many moons ago, laptops came with one or two extra sockets. These were called PCMCIA socets, and allowed you to plug in extra devices (of the sort that would usually go into internal slots in a desktop PC). The most common devices were modems, network cards, etc. The later versions were called cardbus, and (I beleive) even later were just called PC cards. It was also possible to buy a device which fitted into your desktop computer so that you could use the same cards in both your laptop and your PC, but that never really caught on.
If you don't have a laptop or PC that has a Cardbus socket, then the device that you've found is just so much obsolete junk.