Organisation of the Communist Party of the Soviet Union

The organization of the Communist Party of the Soviet Union was based on the principles of democratic centralism.

The governing body of the Communist Party of the Soviet Union (CPSU) was the Party Congress which initially met annually but whose meetings became less frequent, particularly under Joseph Stalin. Party Congresses would elect a Central Committee which, in turn, would elect a Politburo. Under Stalin the most powerful position in the party became the General Secretary who was elected by the Politburo. In 1952 the title of General Secretary became First Secretary and the Politburo became the Presidium before reverting to their former names under Leonid Brezhnev in 1966.

In theory, supreme power in the party was invested in the Party Congress. However, in practice the power structure became reversed and, particularly after the death of Lenin, supreme power became the domain of the General Secretary.

In the late Soviet Union the CPSU incorporated the communist parties of the 15 constituent republics (the communist branch of the Russian SFSR was established in 1990). Before 1990 the communist party organization in Russian oblasts, autonomous republics and some other major administrative units were subordinated directly to the CPSU Central Committee.

At lower levels, the organizational hierarchy was managed by Party Committees, or partkoms (партком). A partkom was headed by the elected "partkom bureau secretary" ("partkom secretary", секретарь парткома). At enterprises, institutions, kolkhozes, etc., they were called as such, i.e., "partkoms". At higher levels the Committees were abbreviated accordingly: obkoms (обком) at oblast (zone) levels (known earlier as gubkoms (губком) for guberniyas), raikoms (райком) at raion (district) levels (known earlier as ukoms (уком) for uyezds), gorkom (горком) at city levels, etc.

...
Wikipedia