How does an air card work on a laptop computer?
An "air card" uses the 3G cell phone network to send data between computers. The card is essentially a cell phone (it has a phone number, for example) minus the screen and the keypad. It has an interface that lets it talk to your laptop - either PCMCIA or USB. Your laptop runs software that dials the phone and moves data on and off the card. The software may also be able to send and receive sms messages.