\the-commands
Whenever you request a new LaTeX counter, LaTeX creates a bunch of behind-the-scenes commands, as well as defining the counter itself.
Among other things, \newcounter{fred} creates a command
\thefred, which expands to “the value of
fred” when you’re typesetting.
The definition of \thefred should express the
value of the counter: it is almost always always a mistake to use the
command to produce anything else. The value may reasonably be
expressed as an arabic, a roman or a greek number, as an alphabetic
expression, or even as a sequence (or pattern of) symbols. If you
need a decision process on whether to re-define
\thefred, consider what might happen when you do
so.
So, for example, if you want your section numbers to be terminated by
a period, you could make \thesection expand with a terminating
period. However, such a change to \thesection makes the
definition of \thesubsection look distinctly odd: you are going to
find yourself redefining things left, right and centre. Rather, use
the standard techniques for
adjusting the presentation of section numbers.
Or, suppose you want the page number to appear at the bottom of each
page surrounded by dashes (as in
“--~nnn~--”).
If you try to achieve this by redefining \thepage, problems will
arise from the use of the page number in the table of contents (each
number will have the dashes attached), and \pageref references
will be oddly modified. In this case, the change of appearance is
best done by redefining the page style itself, perhaps using
package fancyhdr.
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=the-commands