Each document consists of a preamble and a body. The preamble contains information about papersize, textheight, design of the text output, type of text and all other sorts of commands which are valid for the whole document. The body contains your text in which you can use commands that are locally valid. Thus the common syntax of a -file looks like this:
\documentstyle[options]{style}
commands and definitions that are valid for the whole document
\begin{document}
your text and further commands which are valid only locally
\end{document}
[options]: you can use options like: 11pt,12pt...standard textheight is 11pt or 12pt
instead of 10pt; twoside...the output is on two sides;
twocolumn...output is in two columns; german...you can use
german umlaut like ö, ü, ä.
{style}: depending on what your text is all about there's several
text styles available: book, report, article or letter.