Since groff provides such low-level facilities, it can be quite
difficult to use by itself. However, groff provides a
macro facility to specify how certain routine operations
(e.g. starting paragraphs, printing headers and footers, etc.)
should be done. These macros can be collected together into a
macro package. There are a number of macro packages available;
the most common (and the ones described in this manual) are man,
mdoc, me, ms, and mm.