Besides the verb "to be" and gender in general, I think this is one of the most common mistakes people make when they are learning Spanish "Possessive adjectives VS direct/indirect object pronouns", first let me introduce you to possessive pronouns in Spanish:
Possessive adjectives:
Singular Noun Plural Noun Translation Example
mi mis my mi hijo / mis hijos / my children
tu tus your tu perro / tus perros / your dog
su sus their, your, his, her , its su caramelo / sus caramelos / their candy
nuestro/a nuestros/as our nuestro recuerdo / nuestros recuerdos / our memories
vuestro/a vuestros/as your vuestra madre / vuestras madres / your mother
Now, lets see the direct and indirect object pronouns in Spanish:
Direct and indirect object pronouns:
Direct Object Indirect Object Translation Example
Pronoun Pronoun
me me me él me trajo comida / he brought me food
te te you te lo dije / I told you
lo, la le him, her, it, you se lo dije / le dije / I told him
nos nos us él nos trajo comida / he brought us food
os os you os espero / I'll wait for you
los, las les them, you se los dije / les dije / I told them
They look similar right? But so different...