Acá aquí

[poli]

I was under the impression that they have the same meaning but aquí being precisely here while acá is more approximate, but I'm not sure. If they are synonyms is their use determined by region? The same thing goes with allí and allá.

[Rusty]

Have a look here (http://forums.tomisimo.org/showpost.php?p=157120&postcount=8). Remove the postcount parameter in the URL to look at the entire post, which has more explanations.