Skype is a communications application. You can do instant messaging, video conferencing and voice chat with it all for free. In addition you can use their Skype In and Skype Out services to make calls to and from land line phones to your computer. The rates are quite competitive too, especially internationally. I’ve used it numerous times when I travel to Canada. Pair it up with a Bluetooth headset and I was able to call home for only $0.021 a minute. Much cheaper than my cell phone would have been.