This can be a relative URL or fully qualified. The horizontal size of the new window. The vertical size of the new window. Just modify the appropriate value in the args section to be either 0 or 1.
Documents are sets of related information.
The term structure seems to bring some unpleasant imagery with it, especially for creative souls who want to make this medium work in new and innovative ways. But when one is dealing with publishing, the term structure is quite positive. It is the way we put a skeleton behind information, so that the pieces of information work together and make sense as a whole. This series of relationships defines the structure. The meaning of the element is separate from its visual appearance.