Oh it stands for Local Area Network, as for what that is...
LAN is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building using network media. The defining characteristics of LANs, in contrast to wide area networks (WANs), include their usually higher data-transfer rates, smaller geographic area, and lack of a need for leased telecommunication lines. (according to wikipedia.)
its basically like getting two DS' and playing a game wireless-ly right next to each other... just with PCs, or whatever else that can use LAN.
(I probably didn't explain it to well. XD)
Be part of the answer, not part of the problem.
1 Corinthians 13; remember it always.