In Spanish when people are the direct objects of verbs, we need to place an "a" in front of them. We refer to this "a" the Personal A since it is used when persons (human being) are direct objects.

Direct objects are nouns or noun phrases that receive the direct action of the verbs. Look at the first sentence in the table below. "Janet" is the direct object because she is what (who) I "see". Janet is who is being seen(by me.)

In the meantime, Direct objects can be things as well as people; but the personal "a" is used only when the direct object is a person. We put an "a" in front of the noun when it refers to a specific person or specific people.