By this function you can turn-on computer on network, if this computer supporting Wake-on-lan feature. You need MAC number (network card indentifier) of computer for turn-on. You can also assign target IP addres. If you not specify it, then is used broadcast for delivery magic wake-on packet. However broadcasts workinh only on your local network. When you need to wake-up computer on another network, you must specify any existing IP addres on same network segment as targeting computer.
If you want to wake on lan to other computer, maybe this thread is can help you:https://www.delphipraxis.net/95163-wake-lan-wol-fuer-delphi-2007-indy.html
http://synapse.ararat.cz/doc/help/synamisc.html