The Cuttlebug comes with all the plates you need for cutting and embossing.
If you use Nestabilities and some other kinds of products not specifically made for Cuttlebug, you will need an extra mat to emboss.
Spellbinders sells a tan mat made especially for Nesties, but you can also get good results with a red plumbers gasket sheet that you can buy at Home Depot or other hardware stores.
Here's my favorite tutorial by GinaK about using the Nesties in the Bug:
http://blog.ginakdesigns.com/2008/03...cuttlebug.aspx