When RML is processed, the text that is between brackets, [[" and "]], is processed dynamically. This means that the report will not show what exactly is in between the brackets, but instead will fill that data from within OpenERP. In our company footer, for example, the text [[ user.name ]] tells the reporting engine to replace that text with the user's name. Take a few minutes to look through the RML and identify where there is information contained in these brackets.
Additionally, this dynamic syntax can call custom Python methods as well. For example, [[ display_address(company.partner_id) ]] calls a Python method to correctly format the address for the company header.