The personal a (veo a mi amiga)

In the last lesson you saw conozco *a un actor. That little *a is the "personal a" — one of the most characteristic features of Spanish.

personal 'a' (marks a human direct object)
a

People take a

When the direct object of a verb is a specific person, Spanish puts a right before it. English translates it with nothing at all — it has no meaning of its own; it simply marks that the object is a person.

I see my friend in the park.
Veo a mi amiga en el parque.
The boy helps his grandmother.
El niño ayuda a su abuela.
I know my wife's family.
Conozco a la familia de mi esposa.

Things do not take a

The same verb drops the a when its object is a thing. Compare:

I see my friend's house.
Veo la casa de mi amiga.
I need my mom.
Necesito a mi mamá.
I need the phone.
Necesito el teléfono.

a + el becomes al

The contraction you learned with al and del applies to the personal a too:

I listen to the famous singer.
Escucho al cantante famoso.

Pets count as people

Animals you care about also take the personal a:

The girl looks at her cat.
La niña mira a su gato.

Asking "whom?"

Because the person is marked with a, the question word carries it along: ¿A quién...?

Whom are you helping today?
¿A quién ayudas hoy?