Document class is the first line in every LaTeX file and sets the document type. The three standard classes are article (for papers and short documents), book (for long documents with chapters), and report (for reports and theses). Each class defines default margins, font sizes, section hierarchy, and spacing.
\documentclass{article} \title{My Paper} \author{Author Name} \date{2026-08-19} \begin{document} \maketitle \section{Introduction} Content here. \end{document}
\maketitle generates a title page with title, author, and date. Omit \date{...} to use today's date; use \date{} to omit the date entirely.
Document options modify class behavior. Pass them in square brackets: \documentclass[12pt, twoside]{book}. Common options: 11pt or 12pt (font size, default 10pt), twoside (left/right margins differ for binding), twocolumn (two-column layout), landscape (rotate to landscape). article defaults to single-sided; book defaults to two-sided.
Book documents use chapters: \chapter{Chapter Title} (level 1), \section{Section} (level 2), \subsection{Subsection} (level 3). Articles use \section, \subsection, \subsubsection (no chapters). Reports are similar to articles.
Front matter in books uses \frontmatter, \mainmatter, \backmatter to set page numbering and numbering reset:
\documentclass{book} \begin{document} \frontmatter % i, ii, iii, iv (Roman numerals) \chapter{Preface} \mainmatter % 1, 2, 3, ... (Arabic numerals, chapter 1 = page 1) \chapter{Introduction} \backmatter % continues numbering, no chapter numbers \chapter{Appendix} \end{document}
Without \frontmatter and \mainmatter, all pages use the same numbering scheme.
Abstract in articles: use the abstract environment:
\begin{abstract} Summary of paper. \end{abstract}
This generates a centered, indented block. Books don't have a standard abstract command; create one manually or use a custom environment.
Table of contents is generated automatically from section headings:
\tableofcontents
This must be compiled twice to resolve references (first pass generates .toc file, second pass reads it). The TOC appears where you place this command—usually after \maketitle but before the first section.
Starred versions like \section*{Unnumbered} create sections that don't appear in the TOC and aren't numbered.