If a verb has a direct object, it can also have an indirect object. An indirect object tells to whom or for whom the action of the verb was done.
What are indirect objects?
Subject - Verb - Indirect Object - Direct Object
Jorge - mailed - Clarice - a letter. (To whom did he send it? To Clarice)
Julia - bought - her sister - a bicycle. (For whom did she buy it? For her sister.)
Indirect objects are usually living beings like people or animals, but direct objects can be either people or things. If a verb has only one object, it will be a direct object.
Indirect objects usually come between the verb and the direct object. It is possible to restate these sentences using the proposition to and for. While we can still think of the word following the proposition as an indirect object, some grammarians would say that the indirect object has instead become the object of a preposition.
Subject - Verb - Direct Object - Indirect Object
Jorge - mailed - a letter - to Clarice.
Julia - bought - a bicycle - for her sister.