Indirect objects are the nouns in a phrase for whom or to whom the action of the verb happens. In the sentence “I brought him an apple” the indirect object is “him”. “An apple” is the direct object and “I” is the subject.

I	bought	him	an apple
Subject	Verb	Indirect Object	Direct Object

When a personal pronoun is used as an indirect object in Spanish they are generally the same as the direct object pronouns with the exception of the third-person. In that case le is used for lo/la and les for los/las:

   First-Person
   Pásame la pelota.
   Pass me the ball.

   Third-Person
   Él le pasa la pelota.
   He gives him/her the ball.

Also, it is important to note that le and les can also be translated as "you" in the formal address - singular and plural. This is the the third-person conjugation of verbs being used for the formal first-person address.