Spanning Multiple Rows or Columns in Tables in LaTeX

gistfile1.tex

\usepackage{multirow}
 
...
 
\begin{table}[H]
   \begin{center}
      \caption{Example}
      \label{tab:example}
      \begin{tabular}{lcc}
            Column A & \multicolumn{2}{c}{Columns B and C} \\
            x & y & z \\
      \end{tabular}
   \end{center}
\end{table}