Sometimes the doc is just confusing without proper background knowledge mentioned in the manual (Info). How to jump to the manual from the help buffer?
What @Tobias said.
Or if you use library
*Help* buffers provide a link to help from the manuals. Option
help-cross-reference-manuals in that library lets you decide the behavior:
help-cross-reference-manuals is a variable defined in
help-fns+.el. Its value is
Manuals to search, for a
*Help*buffer link to the manuals. A cons.
The car is a list of manuals to search, or the symbol
all, to search all. If
nil, then do not create a cross-reference link.
The cdr is a boolean:
nilmeans search the manuals, then create a cross-ref link: create it only if some search hits are found.
nilmeans create a cross-ref link without searching manuals first (but only if there are some manuals to search).
You can customize this variable.
For more information check the manuals.
The last line of that
*Help* output is what this feature adds (to all
*Help* buffers). The word "manuals" is a link (as is the word "customize", as usual).
The option value lets you choose whether to search manuals before displaying the
*Help* or only when you click the
manuals link. The default behavior is the latter.