It's a common way to ask someone if they speak Spanish in Spain and some parts of Latin America.
Here's a breakdown:
* Hablas: This is the informal form of the verb "to speak" (hablar) in the second person singular.
* Castellano: This refers to the Spanish language, specifically the variety spoken in Spain.
It's important to note that "castellano" is not used in all Spanish-speaking countries. In many parts of Latin America, "español" is the preferred term for the language.