The Council of the European Union forms (along with the European Parliament) the legislative arm of the European Union (EU). It contains ministers of the governments of each of the member-states of the EU.
The Council is assisted by COREPER, which consists of representatives of the member-state at the level of diplomats or high-level civil servants. COREPER generally prepares the Council agenda, and negotiates minor and non-controversial matters, leaving controversial issues for discussion by the Council.
While legally speaking the Council is a single entity, it is in practice divided into several different councils, each dealing with a different functional area. The General Affairs Council is the most important of these, containing Foreign Ministers. Each council contains a different type of minister: e.g. the Agriculture Council contains Agriculture Ministers, and so on.
The Council has a President and a Secretary-General. The President of the Council is the Foreign Minister of the state currently holding the Presidency of the European Union; while the Secretary-General is a civil servant, the head of the Council Secretariat. The Secretary-General also serves as the High Representative for the Common Foreign and Security Policy (CFSP).