A registration certificate (Anmeldebestätigung or Meldebestätigung) proves that you live at a certain address. You get an Anmeldebestätigung when you register your address (the Anmeldung). You get it during the appointment.
![A Meldebestätigung issued in Berlin Meldebestätigung issued in Berlin](https://allaboutberlin.com/images/Meldebescheinigung_Berlin.jpg)
You might need an Anmeldebestätigung to open a bank account, get a cellphone contract, and many other things.