What is $\small \LaTeX$ ?

$\LaTeX$ is a high-quality typesetting system; it includes features designed for the production of technical and scientific documentation. $\LaTeX$ is the de facto standard for the communication and publication of scientific documents. $\LaTeX$ is available as free software.

For full documentation visit latex-project.org.

\documentclass{book}
\begin{document}
...
\end{document}

$\small \LaTeX$ Document Classes

Some of $\LaTeX$ document classes are:

article
book
report
standalone
letter
IEEEtran
slides
beamer

Packages in $\small \LaTeX$

A package is a file or collection of files containing extra $\LaTeX$ commands and programming which add new styling features or modify those already existing. $\LaTeX$ offers a lot of functions by default, but in some situations it can become in handy to use so called packages. To import a package in $\LaTeX$, you simply add the \usepackage directive to the preamble of your document:

\documentclass{article}

\usepackage{PACKAGENAME}

\begin{document}
...
\end{document}