The Schufa (https://en.wikipedia.org/wiki/Schufa ) provides data for their partners/customers on your credit rating and credit score.

Banks will usually not give you an account and shops won't give you credit if your rating is bad. For example, you are so late to pay your bills that the creditor has involved collection agencies or the courts to get their money.

Landlords will more often than not demand a document from the Schufa (supplied at your own expense) to consider you eligible for renting a flat or a house.

edit: grammar