I am using odoo on version 8 and 12 and I'm looking for documentation with all OpenERP classes that could be used on Odoo. Everything I know about them is for some examples I found on Odoo files like "Odoo8/addons/hr/hr_view.xml". We can find the next code on that file:

<form string="Employee">

                    <sheet>

                        <field name="image_medium" widget='image' class="oe_left oe_avatar"/>

                        <div class="oe_title">

                            <label for="name" class="oe_edit_only"/>

                            <h1>

                                <field name="name"/>

                            </h1>

                            <label for="category_ids" class="oe_edit_only" groups="base.group_hr_user"/>

Exploring the odoo files I can find classes that begins with "oe_" everywhere, but I could not find documentation about it anywhere. Could you help me.