When we use "a"
"La mujer está visitando paris" and "La chica está visitando a su amiga"
When we use "a" in these kind of sentences?Im a little bit confused about usage of "a". Please sb explain it to me Thanks
2 Answers
In this case it's called the personal 'a' and goes in front of the 'direct object' in a sentence when it is a person (or sometimes a pet if it's considered to be part of the family jeje).
Here's a lesson on direct objects if you're unsure what they are.
And here's one on the personal 'a' and another on other times that the 'a' is used in Spanish.

But you do not use it after the verb "tener": Ella tiene tres niños (she has three children). Also not used if the person(s) is/are not definite: Esta tienda falta empleados (this store lacks employees).