Often, but not always, a printed document should be designed so that it can be read sequentially. People tire of flipping back and forth to find information that should be presented to them as they need it.
However, in any document, some information will be too detailed for the current context, or incidental to it; use cross-references to provide access to such information. Also, an online help system or a reference manual is not like a novel; few read such documents in sequence from beginning to end. Instead, people look up what they need. For this reason, such creations should contain many cross references to help readers find other information that they may not have read.
In a printed manual, a cross-reference results in a page reference, unless it is to another manual altogether, in which case the cross-reference names that manual. In Info, a cross-reference results in an entry that you can follow using the Info ‘f’ command. (See Following cross-references in Info.) In HTML, a cross-reference results in an hyperlink.
The various cross-reference commands use nodes (or anchors,
@anchor) to define cross-reference locations.
TeX needs nodes to define cross-reference locations. When TeX
generates a DVI file, it records each node’s page number and uses the
page numbers in making references. Thus, even if you are writing a
manual that will only be printed, and not used online, you must
@node lines in order to name the places to
which you make cross-references.