As mentioned previously. Yodl's input consists of text and of commands.  Yodl
supports a number of built-in commands which may either be used in a Yodl
document, or which can be used to create a macro package.

Don't despair if you find that the description of this section is too
technical. Exactly for this reason, Yodl supports the macro packages to make
the life of a documentation writer easier. E.g., see chapter ref(macropackage)
that describes a macro package for Yodl. 
