From the Wikipedia page 
A bairro (lit. quarter, Portuguese pronunciation: [ˈbajʁu]) is a community or region within a city or municipality of Brazil. Regions referred to as bairros exist in most major Brazilian cities. Related English words include neighborhood, district, borough or subdivision. Bairro, a Portuguese word, is cognate with Germanic berg, burg, borg, burgh, borough, etc.; and Spanish barrio, all of which descend from the same Proto-Indo European root.
In Brazil, the word is frequently applied to urban areas in cities, in which the bairros are generally defined only unofficially and have rough borders, without any official administrative function. Some cities' bairros, however, have defined territorial limits set by the municipal government, but most follow popular definition by its citizens.
In Portugal, subdivisions in only a few densely populated urban regions are called bairros, though these do not have any administrative power. An example is the Bairro Alto in Lisbon. Freguesia is the more common subdivision in Portugal.
In Mozambique, bairros are administrative subdivisions of urban districts with important functions in the identification of the residents and determine the attributes of the area in regard to construction or agriculture, much like zoning. They are directed by secretários.