if you have a mic internal or external, you can tell your computer to do things!! like say "get new mail" and it will open the application mail and check for you!!
first you have to configure it to your voice.
go to system prefs and then to speech, from there you should be able to turn this on canfigure your vioce and... yea
a little thing will pop up when you activate it, and then easyly you can go and click the arrow facing down and click the "open speech commands menu" there is the different things you can say!!!
neat isnt it?