A Fiktionsbescheinigung is a temporary residence permit. It lets you stay in Germany while you wait for another residence permit. For example, the Ausländerbehörde can give you a Fiktionsbescheinigung if your old residence permit expires soon, and your new residence permit is not yet approved.

You can't get a Fiktionsbescheinigung if you have a Schengen visa1. A Fiktionsbescheinigung sometimes allow you to travel outside of Germany, but not always1.