A direct object is the direct recipient of the action of a verb.
I invite the boys. Whom do I invite? The boys.
He reads the book. What does he read? The book.
The nouns boys and books are direct objects. They answer the question what? or whom? Verbs that take a direct object are called transitive verbs. Verbs that do not take a direct object (she walks, I sleep) are intransitive.
Direct object pronouns replace direct object nouns.
I invite the boys. I invite them.
He reads the book. He reads it.
In Italian the forms of the direct object pronouns (i pronomi diretti) are as follows:
SINGULAR
PLURAL
mi me
ci us
ti you (informal)
vi you (informal)
La you (formal m. and f.)
Li you (form., m.)
Le you (form., f.)
lo him, it
li them (m. and f.)
la her, it
le them (f.)
A direct object pronoun is placed immediately before a conjugated verb.
Se vedo i ragazzi, li invito. (If I see the boys, I’ll invite them.)
Compra la frutta e la mangia. (He buys the fruit and eats it.)
In a negative sentence, the word non must come before the object pronoun.
Non la mangia. (He doesn’t eat it.)
Perchè non li inviti? (Why don’t you invite them?)
The object pronoun is attached to the end of an infinitive. Note that the final –e of the infinitive is dropped.
È importante mangiarla ogni giorno. (It is important to eat it every day.)
È una buon’idea invitarli. It’s a good idea to invite them.
It is possible, but not necessary, to elide singular direct object pronouns in front of verbs that begin with a vowel or forms of avere that begin with an h. However, the plural forms li and le are never elided.
M’ama, non m’ama. (Mi ama, non mi ama.). (He loves me, he loves me not.)
Il passaporto? Loro non l’hanno (lo hanno). (The passport? They don’t have it.)
A few Italian verbs that take a direct object, such as ascoltare, aspettare, cercare, and guardare, correspond to English verbs that are used with prepositions (to listen to to wait for, to look for, to look at).
Chi cerchi? – Cerco il mio ragazzo. Lo cerco già da mezz’ora!
(Who are you looking for? – I’m looking for my boyfriend. I’ve been looking for him for half an hour!)
Object pronouns are attached to ecco to express here I am, here you are, here he is, and so on.
Dov’è la signorina? – Eccola! (Where is the young woman? – Here she is!)
Hai trovato le chiavi? – Sì, eccole! (Have you found the keys? – Yes, here they are!)
From:https://www.dbfei.com/Article/yidaliyu/201311/7732.html