Hola Susan
Lo, la, los and las are direct object pronouns, i.e pronouns that replace a person/people or a thing/things and they receive the action from the verb directly. Generally you spot them by asking the verb the question What? or Who?
See the following examples:
"Roberto compró pan" --> "Roberto lo compró" (What did Roberto buy? -bread [direct obj]
"Roberto llamó a Claudia" -->"Roberto la llamó" (Who did Roberto call?) -Claudia [direct obj]
lo and la are replacing pan and Claudia and they are both direct object pronouns.
Le and les are indirect object pronouns, i.e pronouns that replace a person/people (not things) and they receive the action from the verb indirectly. Generally you spot them by asking the verb "to whom"? or "for whom"?
See the following examples:
"Roberto compró flores para Claudia" --> Roberto le compró flores (For whom did Roberto buy flowers? -for Claudia, for her. [indirect obj]
"Roberto dio dinero a sus hijos" --> "Roberto les dio dinero" (To whom did Roberto give money? -to his children, to them. [indirect obj]
I hope this clarified your doubts.
Gracias y saludos
Inma
