Veo la película. La veo.
English: I see the movie. I see it.
Direct object pronouns in Spanish are words that replace the noun directly receiving the action of the verb, so you don't have to repeat the noun.
Use direct object pronouns in Spanish when you want to avoid repeating the direct object in a sentence, especially if it is already known or mentioned before.
Veo la película. La veo.
English: I see the movie. I see it.
¿Tienes el libro? Sí, lo tengo.
English: Do you have the book? Yes, I have it.
Nos llaman por teléfono.
English: They call us on the phone.
¿Me escuchas?
English: Do you hear me?
Voy a comprarlo.
English: I am going to buy it.