All students applying for German Visa needs to submit an One page cover letter / Statement of Purpose (SOP).
The SOP must contain
Who you are and what qualifications you holds and for which purpose you are applying for the VISA
Why you want to go to Germany (Course & Country) & how it suits your purpose of visit
Requesting Visa for the above purpose and documents submitted for the same (as BULLETs)
This SOP then needs to be officially translated in German (this could be done at Goethe Institutes & by other recognized German translators)