Ever wanted to come home and have your computer already powered-up, loaded, and ready to go? You could do this by setting up a scheduled Power-ON through BIOS, but maybe you have an erratic schedule…Then what? You could come home at 3:00, or maybe as late as 12:00, and you do not want your computer running needless hours. The solution for you would be the technology known as Wake on LAN (WOL). WOL works like this, when your computer shuts down, some power is reserved for your NIC card (Network Interface Controller). At this point, the controller waits for the “magic packet”. What this is, is a special packet, with some special code, just for your specific card. Upon the arrival of this “magic packet”, the listening computer receives this packet, checks it for the correct information, and then boots if the Magic Packet is valid. You can google if your network card was WOL capabilities, and just about every IBM laptop should have it.

Read more at http://en.wikipedia.org/wiki/Wake-on-LAN