The basic "barebones" idea of digging is you register on that site. Then you visit the link I gave:
http://www.digg.com/design/Free_Webm...,_Tutorials...

Then you will see that by the number on the left it will show the "# of diggs" and a link for you to "digg" a story. When you click it then you have "dugg the story" and you get your free text link.

Digg is a very very high traffic "tech" site just like what slashdot is and basically if a site gets enough "diggs" then it will be promoted to the front page news.