This is a social bookmarking button, which allows you to save links to your favourite social Internet or bookmarking sites, facebook, myspace  or digg etc…  you can also content of interest share with friends. Its easy go back and give it a go…  you will find a list of sites which allow you to share content …  just  like the list bellow, you will also find a video explaining social bookmarking more detail.

Social boohmarking in plain english