\documentclass{article}
\usepackage{caption}
\begin{document}
\begin{table}
\caption{Acronyms}
  \centering
  \begin{tabular}{l r }
    \hline
    % after \\: \hline or \cline{col1-col2} \cline{col3-col4} ...
    A4 & Fourth Generation \\
    AAA & Authentication, Authorization, Accounting \\
    APDV  & Application Protocol Data Unit \\
    \hline
  \end{tabular}
  \label{TAB1.ACC}
\end{table}
\end{document}