[Resuelto] Language dialect

Background of the issue:
I'm using Spanish as a language on my site enlace oculto and would like to know if the default version will be the European version used in Spain.

Symptoms:
Uncertainty about which Spanish language variant is set as default.

Questions:
Will the default Spanish language be the European version used in Spain?
If not, what should the variant be to use, for example, es-es?