Ich habe einen Apfel.
English: I have an apple.
The Akkusativ (accusative case) in German is used to show the direct object of a sentence – the person or thing that receives the action.
Use the Akkusativ when you want to say who or what is directly affected by the action of the verb. It answers the question 'wen?' (whom?) or 'was?' (what?).
Ich habe einen Apfel.
English: I have an apple.
Wir sehen die Katze.
English: We see the cat.
Er kauft das Auto.
English: He buys the car.
Sie liebt ihren Bruder.
English: She loves her brother.