Menus contain pointers to subordinate nodes. In Info output,
you use menus to go to such nodes. texi2any can output menus in
HTML output, but does not do so by default
(see Other Customization Variables, under FORMAT_MENU).
Menus have no role in printed manuals or other output formats.
Menus are automatically generated by texi2any when outputting
Info for nodes followed by a sectioning command, without an explicit
@menu block, and with automatic pointers.
It is often more convenient to let texi2any generate
menus for you, as you do not then have the burden of updating menu
blocks in your Texinfo source when you add, remove, or relocate nodes.
In the usual case of a hierarchically organized manual with sectioning
commands associated with nodes, and with node pointers left out, you
should only write menus if you want exact control over the contents
and formatting of menus in Info.