The guys from Commoncraft have built a reputation in making things clear in a very short time using video.
In this short video (2.38 min) they give a good basic explanation of what the power of LinkedIn is. Of course LinkedIn is much more than that, especially now with the group discussions, but this is a good start if you have never heard of LinkedIn before.
A good networking practice is to share relevant information with your network (and in the meanwhile you keep in touch and maintain your network). So feel free to share this with the people from your network that haven’t heard of LinkedIn yet.
Have a great networking week !