Recently I've started seeing references to the term 'Cicerone' pop up around the internet; generally, they are described as a 'Beer Sommelier' and the subject is left at that.
I'd like to understand the role a little bit better. What exactly does a cicerone do? If I encounter one in a restaurant, what sort of knowledge can I expect her to have? Is there a certification or credential of some sort that they're expected to receive? What sort of training is required?