D.O. stands for Designation of Origin (in catalan: Denominacio d’Origen), which essentially refers to the area where a wine comes from. To put it simple, a wine is related to a D.O. the same way a citizen is related to his/her country. Every single D.O. has its own land and climate characteristics that make their wines different from the rest. Every D.O. is governed by a Regulatory Body (Consell Regulador) whose members are elected from the wineries that make that specific D.O. and their mission is to ensure that the best practices and quality procedures are followed by all its members.
There are 12 D.O.’s in Catalonia. You can locate them in this map of Catalonia: http://catalanwinesusa.com/catalan-dos/
