I love fish, I love Chinese and Japanese food, but I have no idea what's what in the sushi world. I had a raw tuna appetizer recently at a restaurant and it was to die for. It tasted like the best fillet mignon I've ever had with ginger and a sweet/spicy sauce. We have a new sushi restaurant in our area and everything looks so pretty, but I don't know what anything is? What is the black, flat stuff that it's rolled in? Seaweed? What should a beginner order? How do you eat it?