As far as I know it is to add emphasis to a paragraph, so class Lead would be used in the paragraph tag. The paragraph tags would of course be inside the Body tags. I don't know if Copy is just a reference to the text, i.e. like from the Newspaper when they refer to a story in the paper as "Copy", and not actually a class.
"Anyone can do any amount of work, provided it isn't the work he is supposed to be doing at that moment" Robert Benchley, 1930