"Talking" means that you're not together, but you are in negotiations to get together and are feeling each other out. As of now, there are no commitments and you could for instance see another girl, however it is understood that seeing another person would seriously endanger negotiations with the one you are "talking" to. Anyone who wants to get past the "talking" stage with a person would be advised to treat the other person as if a serious relationship already existed. If that is done, after an amount of trust building time, the relationship will automatically be "established". Neither of the two parties will know when that line is crossed but will just eventually come to the realization that it was crossed weeks or months ago.
hope that helps