That's a very broad question...it's like saying, tell me more about the CD-Rom on my PB. 32-Bit Cardbus PCMCIA cards can do just about anything. Wired/Wireless networking, storage, usb, digital video, etc...the list goes on. Can allow you to connect everything from a external hard drive, to a cell phone, to a dvd drive...right to the computer.
Do a little more research on PCMCIA cards...and you'll find the info you need.