The most regular use of the Dative Case in Russian, is when it is used to express an indirect object. The Dative Case can loosely be translated into English as 'to' or 'for', but as these words have many meanings in English, a more in depth explanation is necessary. The indirect object is the person or thing which is affected by a verb, for example;
'I gave the book to him' or 'I gave him the book'.
In this sentence, 'him', would be in the Dative Case. In the second example, it is not as obvious in the English that 'him' would be an indirect object but both sentences would require the word 'him' to be in the Dative Case when translated into Russian and as such both would be translated in the same way:
'Я дал ему книгу'.
This is the most basic use of the Dative Case, although there are many others which can be covered in future lessons.