Teaching German at all levels, a regular task is to explain grammatical cases to my students, who tend to see them as alien concepts, but cases in German are easily explained.
Genitive and Nominative
German has four cases: nominative, accusative, dative and genitive. The genitive is the easiest: it donates possession. The nominative case is reserved for the subject of a sentence, the person or thing that specifies how a verb is conjugated.
Accusative and Dative
The accusative is the person or thing receiving the action of the verb – it is the object of the sentence. The dative is the beneficiary (indirect object) of any action in a sentence. English also has cases, but nouns are no longer declined, dependent on the case. Look at this simple sentence, for example:
I am making breakfast for my wife’s parents.
The subject is ‘I’ – I am left to do the work. The indirect object is ‘my wife’s parents’ – the beneficiary – they are going to eat breakfast. The direct object is the breakfast – that is what is being made. And the genitive is my wife – because she is the one to whom the parents ‘grammatically’ belong.
Think German is complicated? Try learning Russian with six cases or Polish, which has seven cases.