Direct and indirect objects are key parts of building sentences that you should understand. Here we will look at the key difference between them.
The object of a sentence refers to someone or something in relation to the subject’s action of the verb.
A direct object is the receiver of the action within a sentence and it answers the question "who?" or "what?".
So in the first case, the action (the verb) is the marking and it is the homework that is receiving this action i.e. it is being marked. In the second case, the receiver of the action - the shouting (verb) - is Susan, so Susan is the direct object.
In order to have an indirect object in a sentence, there must be a direct object.
The indirect object is the recipient of the direct object. Or in other words, it identifies to or for whom or what the action of the verb is performed.
The direct object and indirect object will be different people, places or things.
So in the first case, the son is the recipient of the direct object (the present). So the action - buying the present - is being performed for him. In the second case the recipient is Phillip, who is the recipient of the card (direct object).