The indirect object of a sentence is a noun or noun phrase that is secondarily affected by the action of a transitive verb, like "me" in sentence (1):

                 (1) She brings me the food.*

*In English, sentence (2) can also be phrased as:

                 (1a) She brings the food to me.

*In Spanish, this is expressed through either "Ella me trae la comida." or  "Ella me trae la comida a mí."

The direct object and the indirect object are always nouns, noun phrases, or pronouns. Nouns and noun phrases can be replaced by pronouns:

                 (1) She brings it.

                 (2) She brings me the food.

                 (3) She brings me it.

                 (4) She brings it to me.

In Spanish, these sentences would look like this:

                 (1) Ella la trae.

                 (2) Ella me trae la comida.

                 (3) Ella la me trae.

                 (4) Ella me la trae.

When both direct and indirect object pronouns are being used in a sentence, the indirect object pronoun comes first:

                 (4) Ella me la trae.

Let's look at another example.

                 (1) Yo leí el libro.

                 (2) Yo le leí el libro (a la niña).

When

                 (3) Yo se lo leí.