Names given to the Spanish language
Formally speaking, the national language of Spain, the official Spanish language, is the Castilian language (as opposed to regional Spanish languages like Galician, Catalan, Asturleonese and Basque). As such both names, "español" and "castellano", have distinct and independent meanings that may be required for clarity in some specific contexts.
Generally speaking, though, both terms can be used to refer to the (national) Spanish language as a whole, with a preference for one over the other that depends on the context or the speaker's origin. "Castellano" (as well as "Castilian" in English) has another, more restricted, meaning, relating either to the old Romance language spoken in the Kingdom of Castile in the Middle Ages, predecessor of the modern Spanish language, or to the variety of Spanish nowadays spoken in the historical region of Castile, in central Spain.
Peninsular Spanish
Peninsular Spanish (), also known as Spanish of Spain () European Spanish () and Iberian Spanish (), sometimes inaccurately referred to as Castilian Spanish () refers to the varieties of the Spanish language spoken in the Iberian Peninsula, as opposed to the Spanish spoken in the Americas and in the Canary Islands. The related term Castilian Spanish is often applied to formal varieties of Spanish as spoken in Spain. According to folk tradition, the "purest" form of Peninsular Spanish is spoken in the Castilian province of Valladolid, although the concept of "pure" language has been questioned by modern linguists.