LaTeX - Hello world

The simplest (non-empty) LaTeX document:

\documentclass{article}

\begin{document}
Hello world!
\end{document}

A bit more complicated example:

\documentclass{article}

\begin{document}

\author{Marcin Borkowski}
\title{A simple \LaTeX{} document}
\maketitle

\section{The first section}
Probably 90\% of \LaTeX{} users learn it by \emph{copying examples}.
We shall follow that practice.  If example files are not enough---and
it will happen at some point of learning \LaTeX---then one has to
``RTFM'', or ``Read The Friendly Manual'', i.e.\ consult the
\emph{documentation}\footnote{Or ask a friend.}.

Let us notice that the actual layout of a paragraph in the source file is irrelevant:
newlines
are
treated
like
spaces,
except that \emph{two} newlines in a row mean ``begin a new paragraph''.

\end{document}