simple.tex

\documentclass[12pt,fleqn]{article}

\title{Simple \LaTeX{} Document}
\author{Alex Pacheco}
\date{\today}

\begin{document}
\maketitle
\tableofcontents

\begin{abstract}
  In this article we discuss how to create simple \LaTeX{} documents. Topics include structuring a document, list environment, inserting equations and figures, creating tables and more.
\end{abstract}

\section{Section 1}
\subsection{Section 1.1}
\subsection{Section 1.2}
\subsection*{Section nonumber}
\addcontentsline{toc}{subsection}{Section nonumber}
  blah blah blah

\section{Section 2}
\subsection{Section 2.1}
\subsubsection{Section 2.1.1}
\subsubsection{Section 2.1.2}
\paragraph{Paragraph} no numbering for this paragraph
\subparagraph{Subparagraph} no numbering for this subparagraph
\subsection{Section 2.2}
  blah blah blah

\appendix
\section{Appendix A}
\subsection{Appendix A.1}
  blah blah blah

\section{Appendix B}
\subsection{Appendix B.1}
\subsubsection{Appendix B.1.1}
  blah blah blah

\end{document}