Congress, Central Committee and Political Bureau: how plenary sessions fit into the Communist Party of China

Background

The Communist Party of China is holding the fifth plenary session of its 20th Central Committee in Beijing, so the structure behind that name is worth setting out.
The Party's National Congress meets once in five years and elects a Central Committee, which is numbered after the Congress that elected it; the present one is the 20th Central Committee.
Between Congresses the Central Committee meets in plenary sessions, usually once a year, and these are numbered in order, so the fifth plenum is the fifth such full meeting of this Central Committee.
The Political Bureau, or Politburo, acts for the Central Committee between plenums and reports its work to the plenary session.
The General Secretary of the Central Committee is the Party's highest post, and Xi Jinping is the general secretary who chaired the Political Bureau meeting that convened this session.
The Central Military Commission is the Party's top military body, and the session may decide appointments to it.