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.
Andalusian Spanish
The Andalusian varieties of Spanish (Spanish: "andaluz" ; Andalusian: "andalú" ) are spoken in Andalusia, Ceuta, Melilla, and Gibraltar. They include perhaps the most distinct of the southern variants of peninsular Spanish, differing in many respects from northern varieties, and also from Standard Spanish. Due to the large population of Andalusia, the Andalusian dialects are among the ones with more speakers in Spain. Within Spain, other southern dialects of Spanish share some core elements of Andalusian, mainly in terms of phonetics notably Canarian Spanish, Extremaduran Spanish and Murcian Spanish as well as, to a lesser degree, Manchegan Spanish.