The IBM card is just a rebranded Orinoco card. It Does have an external antenna jack. The jack is on the side of the card and has a cover on it.... the hole for the jack itself is about is big around as a pencil lead. You can prolly pull the cover off with your fingernail or a pair of tweezers or something.
As for pigtails...
They allow you to use an external antenna. The orinoco cards use a propietary antenna jack so you have to buy a pigtail for your card. These can be purchased from www.fab-corp.com as well as the antennas or you can make your own antenna.

http://www.fab-corp.com/K1.htm is the page for the pigtails....bout half way down the page you'll see the orinoco male & femail pigtail. Most people get the male pigtale b/c most antennas have a female end.
You do not HAVE to have an external antenna, but for distance, it sure does help.

Have fun.