A USCIS approval either means that your status has changed to the new status you requested if you are in the U.S., or that that you qualify for the immigration status requested and you are authorized to apply for visa. If you are outside the U.S., the embassy or consulate determines whether you may ask to be admitted to the U.S. by deciding whether you get a visa for the status that USCIS approved. The visa in the passport can be viewed as a pass or ticket to ask for admission to U.S., while the USCIS approval grants permission to be present in the U.S. in a specific nonimmigrant status, or permission to apply for a visa to enter. There are exceptions to this process in the visitor/tourist context, such as the B-1/B-2 visitor visas, which only have a visa application that is processed through a consulate or embassy abroad without having to apply through USCIS.