Direct Object Pronouns (“Pronombres de Complemento Directo”) are a collection of pronouns which point to the person or thing that receives the action of the verb.
Here is the full list of Direct Object Pronouns in Spanish and their meaning in English:
te singular you
lo, la him, her, it, formal singular you
os plural you
los, las them, formal plural you
As we said, these pronouns point to the thing or person receiving (not doing!) the action of the verb.
¿Me quieres? = Do you love me?
Sí, te quiero = I love you.
La tengo en mi casa = I have it at home (“it” referring something of feminine singular, it could be a table for example).
Laura nos conoce = Laura knows us
Os vemos = We see you guys
Los he perdido = I have lost them (“them” referring to something masculine plural, it could be books)
In all of the examples above, the Direct Object Pronouns goes right before the verb. That is their most usual placement, but it depends on the tense of the verb. There are tenses, for which the pronoun is attached at the end of the verb. To study that more in depth please read this post with a full explanation on the placement of Direct, Indirect and Reflexive pronouns.
A bit more on the third person forms: “lo, la, los, las”
Keep in mind that the forms “lo, la, los, las” are used to replace a noun that receives the action of the verb.
And why don’t we just say the noun? The most typical reason is that we have mentioned it before, and we don’t want to repeat it endlessly. That’s why we use a Direct Object Pronoun instead.
-¿Quién tiene el muñeco? = Who has the doll?
– Marta lo tiene. = Marta has it
– ¿Has visto mis gafas? = Have you seen my glasses?
– Sí, las he visto. = Yes, I have seen them.
Conozco la ciudad. La conozco muy bien. = I know the city. I know it very well.