The Dativ is the case of the indirect object.
In "I give it to him": "to him" is Dativ.
"The man is giving the table to the man."
Der Mann gibt dem Mann den Tisch.
The distinction between Dativ and Nominativ/ Akkusativ is clearly visible.
The articles are:
dem/ einem, der/ einer, dem/ einem,
plurals: den/ --.
The plural Dativ noun attaches an -n:
den Geistern,
den Büchern,
den Kartoffeln
Certain verbs and certain prepositions require the Dativ case. This is the case of Nietzsche's book title Die Geburt [...] aus dem Geiste [...].