What do ir and res stand for, apart from being directories in the base module of OpenERP. Most of the errors I see while using openerp show 'ir' or 'res' somewhere in the traceback.
IR = Information Repository
RES = Resource
These are two kinds of data that are stored in OpenERP.
A resource matches something in the 'real world' that you store in OpenERP - to represent information about partners, or products or accounting transactions.
The Information Repository is used to store data needed by OpenERP to know how to work as an application - to define menus, windows, views, wizards, database tables, etc.