"It" in Spanish: lo, la, ello...
It as a subject
Subject pronouns are totally optional in Spanish, we usually don't use them:
They're very clever: Ellos son muy listos or son muy listos
We don't have a word for "it" when it's a subject, so we can never add it:
Ex: It's nice! - ¡Es bonito!
Direct object pronoun
A direct object pronoun refers to a direct object: person or object in the sentence, affected by the verb.
Usually you can find it if you ask the verb "what?":
I buy bread.
What do I buy? Bread.
Bread is the direct object.
If I want to replace "bread", I'd say "it", right? Well, for that kind of "it" we do have a word: lo (masculine) and la (feminine).
I buy bread - Compro pan
I buy it - Lo compro
I want a jacket - Quiero una chaqueta
I want it - La quiero
¿Did you see my dad? - ¿Viste a mi padre?
Yes, I saw him- Sí, lo vi.
We never finish a sentence with a preposition, so if after one we have an "it", we do have a word for it: ello. This is the most common location for it.
Having said that, this happens wherever the location is, not only at the end.
This would be a "concept" or "action" we don't know the gender and that we've mentioned before.
They talk about it - Hablan sobre ello
I'm sure of it - Estoy seguro ello
She complained about it - Ella se quejó de ello
Puedes aprender muchas cosas pero para ello, tienes que leer mucho - You can learn many things but to do it/that, you have to read a lot.
Fill in the gaps with: lo, la, ello or nothing!
A pesar de _____ no estoy convencida - Despite it/that, I'm not convinced.
¿Tienes el cuadro?¿__ puedes traer? - Do you have the painting? Can you bring it?
_____ es una casa preciosa, ____ veremos mañana - It's a gorgeous house, we'll see it tomorrow.
Quieres que aprenda esta lista pero necesito tiempo para ____ - You want me to learn this list but I need time for it/that.
He hablado mucho sobre este cambio pero me gustaría insistir en ____ - I have talked a lot about this change but I'd like to insist on it.