Ich gebe dem Mann das Buch.
English: I give the book to the man.
The dative case (Dativ) in German shows to whom or for whom something is done. It is used with certain verbs and prepositions.
Use the dative case in German to indicate the indirect object of a sentence (the person who receives something), after certain verbs (like 'helfen', 'geben') and after some prepositions (like 'mit', 'zu', 'bei').
Ich gebe dem Mann das Buch.
English: I give the book to the man.
Sie hilft der Frau.
English: She helps the woman.
Wir spielen mit dem Kind.
English: We play with the child.
Er spricht mit den Kindern.
English: He speaks with the children.