In order to apply for a visitor’s visa and if your host in Germany bears your travel costs, an original letter of sponsorship (or so-called “Verpflichtungserklärung,” according to § 68 of the German Immigration Law or "Aufenthaltsgesetz") from your sponsor in Germany must be submitted.
Please note that only the original letter of sponsorship will be accepted. A photocopy or facsimile is not sufficient!
The sponsor in Germany must apply for this standardized letter of sponsorship at the competent immigration office (the so-called “Ausländerbehörde” or “Ausländeramt”), which is usually situated at your sponsor’s local city administration in Germany.
Without an original letter of sponsorship, the visa application will NOT be accepted.