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.
Culture of Uruguay
Spanish is the official language of Uruguay, and is spoken by almost all of the population. The Spanish spoken in Uruguay is more commonly known as Rioplatense Spanish, the same Spanish that is spoken in parts of Argentina. Rioplatense Spanish is known by many in South America as Spanish spoken with an Italian accent, due to Italian effects on modern day Uruguayan society. Minority languages in Uruguay include Italian, French, German, Hebrew, and other European languages. English is also considered a minority language, though it is more used in the business world. Other languages include Portuguese and "Portuñol", a mixture of Spanish and Portuguese (pidgin language). Both are present in northern regions near the Brazilian border.