A Category D visa is a type of German visa. It’s also called a National Visa. It lets you enter Germany to work, study or start a business.
You must apply for a Category D visa at the German embassy or consulate in your home country.
The Category D visa is only valid for 3 to 12 months. You must convert it to a residence permit at the Ausländerbehörde after you arrive in Germany.
The Schengen visa is not a Category D visa.