Terms

Active cell
The selected cell in which data is entered when you begin typing. Only one cell is active at a time. The active cell is bounded by a heavy border.
Block
A block is an element that takes up the entire available width. A block is delimited by line breaks before and after it.
Inline
An inline element takes up as much width as necessary, and does not force line breaks.
Inline XML element
Inline elements are elements which appear in a mixed-content context (parents with both non-whitespace text and elements).