Barrio is a Spanish word that means neighbourhood, district or suburb.
In the city of Buenos Aires there are 48 barrios, named as follows:
Agronomía, Almagro, Balvanera, Barracas, Belgrano, Boedo, Caballito, Chacarita, Coghlan, Colegiales, Constitución, Flores, Floresta, La Boca, La Paternal, Liniers, Mataderos, Monte Castro, Montserrat, Nueva Pompeya, Núñez, Palermo, Parque Avellaneda, Parque Chacabuco, Parque Chas, Parque Patricios, Puerto Madero, Recoleta, Retiro, Saavedra, San Cristóbal, San Nicolás, San Telmo, Vélez Sársfield, Versalles, Villa Crespo, Villa del Parque, Villa Devoto, Villa Lugano, Villa Luro, Villa Mitre, Villa Ortúzar, Villa Pueyrredón, Villa Real, Villa Riachuelo, Villa Santa Rita, Villa Soldati, Villa Urquiza
It is also common to hear people mention certain other zones in Buenos Aires such as Barrio Norte (area north of Av. Córdoba into parts of Recoleta and Palermo), Abasto (parts of Almagro and Balvanera near the Abasto shopping mall), Once (parts of Balvanera south of Av. Córdoba), Congreso (area surrounding the Congress square), and parts of Palermo such as Palermo Chico, Palermo Viejo, Palermo Hollywood and Palermo Soho.
Barrios in Buenos Aires are grouped into administrative areas called Comunas (Communes).
A Barrio cerrado has a slightly different meaning - it generally refers to a neighborhood enclosed in walls with security at the entrance. i.e. a community where wealthier people live. In a bit of a misplay of the English word, barrios cerrados away from the city are often called "countries" in Argentina (country as in countryside).