When you are about to pick a product from a supermarket shelf you are supposed to check first its brand, features and price before taking any decision. In some cases, where brand is not decisive, you rely on the retailer endorsement to support your decision.
Unlike other products, most foodstuffs and agricultural products don’t have any brands or support from any organization. That makes harder to pick the best quality (or value for money) product out of a wide range of supply, only based on our knowledge or previous experience.
Since 1992, the European Union promotes among foodstuff and wine producers to get associated in Protected Designations of Origin (PDO), in Spanish "Denominación de Origen Protegida (DOP)", that help them to market their products better, while providing them legal protection from product name misuse or counterfeit.
From the consumer point of view, the PDO framework identifies products that are grown, produced, processed and prepared in a specific geographical area, using the recognized know-how of local producers and ingredients from the region concerned. Producers must adhere to a precise set of specifications defined by the regulatory body which in turn is approved and supported by the EU.
Note: there is another slightly different designation as well, called Protected Geographical Indication (PGI) that does not require to grow/supply all the ingredients on the same geographic area, focusing on how they are processed and prepared.
There are PDO in almost all EU member countries, although more than 80% of them are registered in 6 countries: Italy, France, Spain, Greece, Portugal and Germany. In Spain, they are called Denominación de Origen Protegida (DOP). In this link you can find them all.
There are 102 PDO in Spain and 88 PGI, of which we highlight just a few, as an example