When the verb object is animated, it´s necessary to use before the
preposition
a. Compare:
Voy a ver ___ una película – I am going to see a
moovie (moovie isn´t animated, so no special preposition is needed)
Voy a ver a una amiga – I am going to see a
friend (as "a friend" is animated, you must use before a)Conozco __ una cafetería – I know a coffee-shop
Conozco a una persona – I know a person
The preposition a often appears with these verbs:
querer a – to love somebody
conocer a – to know somebody, to get acquainted with somebody
ver a – to see somebody