okay, you might think this is a little obvious, but i'm new to this

how did they get the dots at the bottom of each tier in this picture?

http://www.cakecentral.com/modules.php?name=gallery&file=displayimage&pid=1428123

and what kind of icing is it?

That's regular buttercream icing and you just use a round tip..........a number 10 should do the trick and you hold the tip in place and pipe the dot and then drag the icing and pipe another dot and so forth.

here, look at this:

http://www.wilton.com/technique/Bead

okay thanks much!