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.
Hispanic and Latino Americans
Hispanics have revived the Spanish language in the United States. First brought to North America by the Spanish during the Spanish colonial period in the 16th century, Spanish was the first European language spoken in the Americas. Spanish is the oldest European language in the United States, spoken uninterruptedly for four and a half centuries, since the founding of Saint Augustine, Florida in 1565. Today, 90% of all Hispanics and Latinos speak English, and at least 78% speak fluent Spanish. Additionally, 2.8 million non-Hispanic Americans also speak Spanish at home for a total of 41.1 million.