I don't really know the complicated lingo stuff, but my favorite order is a:
  Grande Non-Fat Tazo Chai 
In plain language, that's a medium black tea latte (chai is an indian tea that tastes kinda like cinnamon and nutmeg - yum!) made with skim milk. 
I love it but I only get it as a special *treat* because it's about $4. Too pricey for a regular vice.