This is the 13133rd most frequent Spanish word.
preguntarle
"Preguntarle" means "to ask him/her."
In this sentence, 'preguntarle' indicates the act of asking a question to a third person, 'le' being the indirect object pronoun referring to him/her.
Voy a preguntarle sobre su viaje.
I am going to ask him/her about their trip.
Here, 'preguntarle' suggests posing a question to the person being referred to directly, again with 'le' as the indirect object pronoun.
¿Por qué no intentas preguntarle directamente lo que ocurrió?
Why don't you try asking him/her directly what happened?
In this instance, 'preguntarle' involves the context of inquiring from 'him/her' about a specific topic.