I am a comics creator and learned a bit of storyboarding from Katz's book, Directing Shot By Shot (highly recommended). This is the first time I've noticed such a big link between comics and animation.

What does 'book 1' signify? I see the term 'book' in all of your roughs.

Dekatrops_Loris said:
What does 'book 1' signify? I see the term 'book' in all of your roughs.

Book equates to what's basically a "layer" in drawing software.
The background is the furthest back element of the background, but for example, if a character is walking behind a tree (which is not a cel), then the tree will usually be a "book", as its separate from the background, for practical reasons, like a cel appearing behind it, composition elements like fog etc.
You can think of it as set pieces in a theater. The backdrop is the background, the different set-pieces will be "books", and the characters will be "cels".