In a nutshell, the acreditaciones are qualifications provided by an official agency certifying that the holder can have certain position within the university system. This agencies can be the ANECA, whose acreditaciones are valid for every university, or the regional agencies like AQU (Catalonia) or UNIBASQ (Basque Country), whose acreditaciones are equally valid in their regions.
Profesor Contratado Doctor/Professor Agregat:
Profesor Titular:
Catedrático: