It's a really simple block for adding links to your social media presences to your website.
Add the block, choose the social media services to display by adding the address (for example http://twiter.com/formigo), and checking its checkbox to make it live.
You can reorder how icons display on your site by dragging services up and down by their arrow icons.
There are also options to left align the icon set on your page, open services in new windows, and indeed 'no-follow' the links off your site to these services.
Once you save the block you can choose different icon sets using the supplied custom templates. Check out the screen grabs for available designs.