Counters
Everything LaTeX numbers for you has a counter associated with it. The name of the counter is often the same as the name of the environment or command associated with the number, except with no backslash (\). Thus the \chapter command starts a chapter and the chapter counter keeps track of the chapter number. Below is a list of the counters used in LaTeX’s standard document classes to control numbering.

part            paragraph       figure          enumi
chapter         subparagraph    table           enumii
section         page            footnote        enumiii
subsection      equation        mpfootnote      enumiv
subsubsection

The mpfootnote counter is used by the \footnote command inside of a minipage (see minipage).
The enumi through enumiv counters are used in the enumerate environment, for up to four nested levels (see enumerate).
New counters are created with \newcounter. See \newcounter.

\alph \Alph \arabic \roman \Roman \fnsymbol: Printing counters
All of these commands take a single counter as an argument, for instance, \alph{enumi}. Note that the counter name does not start with a backslash.
\alph 	prints counter using lowercase letters: ‘a’, ‘b’, ...
\Alph 	uses uppercase letters: ‘A’, ‘B’, ...
\arabic 	uses Arabic numbers: ‘1’, ‘2’, ...
\roman 	uses lowercase roman numerals: ‘i’, ‘ii’, ...
\Roman 	uses uppercase roman numerals: ‘I’, ‘II’, ...
\fnsymbol 	prints the value of counter in a specific sequence of nine symbols (conventionally used for labeling footnotes). The value of counter must be between 1 and 9, inclusive.
Here are the symbols (as Unicode code points in ASCII output):

asterisk(*) dagger(‡) ddagger(‡)
section-sign(§) paragraph-sign(¶) parallel(∥)
double-asterisk(**) double-dagger(††) double-ddagger(‡‡)

\usecounter{counter}
Synopsis:

\usecounter{counter}

In the list environment, when used in the second argument, this command sets up counter to number the list items. It initializes counter to zero, and arranges that when \item is called without its optional argument then counter is incremented by \refstepcounter, making its value be the current ref value. This command is fragile (see \protect).
Put in the preamble, this makes a new list environment enumerated with testcounter:

\newcounter{testcounter}
\newenvironment{test}{%
  \begin{list}{}{%
    \usecounter{testcounter}
  }
}{%
  \end{list}
}

\value{counter}
Synopsis:

\value{counter}

This command expands to the value of counter. It is often used in \setcounter or \addtocounter, but \value can be used anywhere that LaTeX expects a number. It must not be preceded by \protect (see \protect).
The \value command is not used for typesetting the value of the counter. See \alph \Alph \arabic \roman \Roman \fnsymbol.
This example outputs ‘Test counter is 6. Other counter is 5.’.

\newcounter{test} \setcounter{test}{5}
\newcounter{other} \setcounter{other}{\value{test}}
\addtocounter{test}{1}

Test counter is \arabic{test}.
Other counter is \arabic{other}.

This example inserts \hspace{4\parindent}.

\setcounter{myctr}{3} \addtocounter{myctr}{1}
\hspace{\value{myctr}\parindent}

\setcounter{counter}{value}
Synopsis:

\setcounter{counter}{value}

The \setcounter command globally sets the value of counter to the value argument. Note that the counter name does not start with a backslash.

\addtocounter{counter}{value}
The \addtocounter command globally increments counter by the amount specified by the value argument, which may be negative.

\refstepcounter{counter}
The \refstepcounter command works in the same way as \stepcounter (see \stepcounter): it globally increments the value of counter by one and resets the value of any counter numbered within it. (For the definition of “counters numbered within”, see \newcounter.)
In addition, this command also defines the current \ref value to be the result of \thecounter.
While the counter value is set globally, the \ref value is set locally, i.e., inside the current group.

\stepcounter{counter}
The \stepcounter command globally adds one to counter and resets all counters numbered within it. (For the definition of “counters numbered within”, see \newcounter.)

\day \month \year: Predefined counters
LaTeX defines counters for the day of the month (\day, 1–31), month of the year (\month, 1–12), and year (\year, Common Era). When TeX starts up, they are set to the current values on the system where TeX is running. They are not updated as the job progresses.
The related command \today produces a string representing the current day (see \today).