Hola Win

Allá and Acá are synomyms of "allí" and "aquí".

Allá and acá are more common in Latin America than Spain.

When we use allá in Spain we refer to "there" but a "there that is quite unreachable and very far away in the distance".

I would say that aquí and acá in Spain are the same, with "aquí" used a lot more often.

Saludos.

Inma