# TexLive Basics

**Every LaTeX document starts with `\documentclass`**, which selects the document type (article, book, report). Then you open the document environment with `\begin{document}` and close it with `\end{document}`. Everything between those tags is your content; everything before (the preamble) defines packages, settings, and commands.

A minimal document compiles and produces a PDF:

```latex
\documentclass{article}
\begin{document}
Hello, world!
\end{document}
```

Save this as `main.tex` and compile:

```bash
pdflatex main.tex
```

This produces `main.pdf`. The `.log` file shows compilation details; `.aux` and `.out` are auxiliary files used during compilation.

Commands in LaTeX start with backslash and take arguments in curly braces (mandatory) or square brackets (optional). `\textbf{bold}` makes bold text. `\textit{italic}` makes italic. `\emph{emphasized}` is context-aware (italic in normal text, upright in italic context). Comments start with `%` and ignore everything to the end of the line.

Most of your editing happens after `\begin{document}`. Everything before that (preamble) configures packages and commands. As documents grow, move preamble to separate files and use `\input{preamble.tex}` to keep things organized.

The first compilation is slow (building caches); subsequent compiles are fast. If you reference labels or citations, compile twice to resolve cross-references: `pdflatex main.tex && pdflatex main.tex`.

Errors stop compilation. Read the `.log` file (or terminal output) for line numbers and error messages. Common errors: mismatched braces, undefined commands, missing packages. See [[texlive-debugging]] for error message reference.