OpenERP documentation uses RST [1] format, which is rendered as HTML or PDF using Sphinx [2]. Build scripts are provided in the documentation tree to easily contribute and manage translations, and to produce the various outputs.

If you are interested in contributing to the documentation, the structure and guidelines are outlined here [3] and [4].

[1] ReStructuredText: http://en.wikipedia.org/wiki/ReStructuredText
[2] Sphinx: http://sphinx.pocoo.org/
[3] How to build the OpenERP Documentation: http://doc.openerp.com/contribute/08_documentation_process.html#building-the-documentation
[4] How to modify/translate the OpenERP Documentation: http://doc.openerp.com/contribute/09_documentation_translation.html