"[T]he national presidency is shared between a Serb, a Croat and a Bosniak, who take turns serving as its chairman every eight months. Modern Bosnia is made up of two ethnically based “entities”, which both have governments and presidents, plus Brcko, an autonomous town. One entity is the Serb-dominated Republika Srpska and the other is the Federation, dominated by Bosniaks and Croats. The Federation consists of ten cantons, each with its own prime minister. All this is ridiculous, say critics. But such complications are hardly unique to Bosnia. The United Kingdom, after all, has four entities, three regional parliaments and a head of state who must be a member of the Church of England. Power in Bosnia lies with the entities and the cantons, not the national government—but something similar happens in Switzerland."

https://www.economist.com/blogs/economist-explains/2017/11/economist-explains