The term "politburo" in English comes from the Russian Politbyuro (Политбюро), itself a contraction of Politicheskoye Byuro (Политическое бюро, "Political Bureau"). Among the remaining Communist states, the Spanish term Politburó was directly loaned from Russian, while Chinese uses a calque (Chinese: 政治局; pinyin: Zhèngzhì Jú), from which the Vietnamese (Bộ Chính trị), and Korean (정치국, 政治局 Jeongchigug) terms derive.
The very first politburo was created in Russia by the Bolshevik Party in 1917 to provide strong and continuous leadership during the Russian Revolution occurring during the same year. However, after the Bolshevik's insurrection in Petrograd, the politburo was dissolved and the Central Committee became the governing body of Russia. During the twentieth century, nations that had a politburo included the USSR, East Germany, Afghanistan, Czechoslovakia and China, amongst others. Today, there are five countries that have a communist politburo system (China, North Korea, Laos, Vietnam, and Cuba).
In Marxist-Leninist states, the party is seen as "the vanguard of the people" and from that legitimizes itself to lead the state. In that way, the party officials in the politburo informally lead the state.
In the Soviet Union for example, the General Secretary of the Communist Party did not necessarily hold a state office like president or prime minister to effectively control the system of government. Instead, party members answerable to or controlled by the people held these posts, often as honorific posts as a reward for their long years of service to the people's party. On other occasions, having governed as General Secretary, the party leader might assume a state office in addition. For example, Mikhail Gorbachev initially did not hold the presidency of the Soviet Union, that office being given as an honour to former Soviet Foreign Minister Andrei Gromyko. Joseph Stalin ruled the Soviet Union for well over a decade before assuming the governmental position of Premier of the Soviet Union during World War II.
Officially, the Party Congress elects a Central Committee which, in turn, elects the politburo and General Secretary in a process termed democratic centralism. Thus, the politburo was theoretically responsible to the Central Committee. Under Stalin this model was reversed, and it was the General Secretary who determined the composition of the Politburo and Central Committee. This tendency decreased to some extent after Stalin's death, though in practice the Politburo remained a self-perpetuating body whose decisions de facto had the force of law.
In Trotskyist parties, the Politburo is a bureau of the Central Committee tasked with making day-to-day political decisions, which must later be ratified by the Central Committee. It is appointed by the Central Committee from among its members. The post of General Secretary carries far less weight in this model. See, for example, the Lanka Sama Samaja Party.