By
default, the LaTeX output uses the class
article.
You
can change this globally by setting a different value for
org-export-latex-default-class or locally by adding
an option like #+LaTeX_CLASS: myclass in your file,
or with a :LaTeX_CLASS: property that applies when
exporting a region containing only this (sub)tree. The class must
be listed in org-export-latex-classes. This variable
defines a header template for each class1, and allows you
to define the sectioning structure for each class. You can also
define your own classes there. #+LaTeX_CLASS_OPTIONS
or a LaTeX_CLASS_OPTIONS property can specify the
options for the \documentclass macro. You can also
use #+LATEX_HEADER: \usepackage{xyz} to add lines to
the header. See the docstring of
org-export-latex-classes for more information.
[1] Into which the values of
org-export-latex-default-packages-alist and
org-export-latex-packages-alist are spliced.