The Republika Srpska (Serbian, Bosnian, Croatian: Republika Srpska, Cyrillic script: Република Српскa, [rɛpǔblika sr̩̂pskaː]) is one of two administrative entities that constitute Bosnia and Herzegovina, the other being the Federation of Bosnia and Herzegovina. The Constitution of Republika Srpska defines it as a territorially unified, indivisible and inalienable constitutional and legal entity of Bosnia and Herzegovina, that independently performs its constitutional, legislative, executive and judicial functions. The National Assembly and the Government of Republika Srpska are based in Banja Luka, although Sarajevo remains the official capital
More information on the Wikipedia page [1]
See also Serbia