Wake-On-Lan (WOL) is an ACPI interface that allows you to turn on your PC on across a Network. Its a nice feature to have if you run a large network. The main use is that if you want to get some data off a PC that is off. By creating network activity to the OFF PC the Network Card then sends a command to the WOL header and turns the PC on, so in a matter of minutes you have the data you wanted. For lazy people this is a must or for system admins who want to turn a group of PC's ON or save a trip. The requirements for this are a WOL header on the motherboard and a 3 pin wire that connects to the motherboard's WOL connector to the NIC's.
FULL STORY @ TECHMOCRACY (http://www.techmocracy.com/extremecooling/acctonnic.shtml)