How to write a table in LaTeX

The tabular environment creates a table.

\begin{tabular}{cc}
Book & 30 \\
Pen & 5
\end{tabular}

Two c in the argument means the table has two columns. If it is ccc, the number of columns is 3. c means each item is centered.

\begin{tabular}{lc}
Book & 30 \\
Pen & 5
\end{tabular}

\begin{tabular}{lr}
Book & 30 \\
Pen & 5
\end{tabular}

\begin{tabular}{lrc}
Book & 30 & 7 New \\
Pen & 5 & 24 New
\end{tabular}