The Council of Ministers is the EU institution which represents the EU member states. It is a many-headed creature and may bring together government ministers from each country, heads of government, ambassadors, or merely government officials.
A summit meeting of heads of government is known as a European Council, while a meeting of ambassadors (or permanent representatives as they are termed) goes under the name Coreper.
Many decisions are made by officials meeting in technical committees and are then merely rubber-stamped by ministers.
Unlike the Commission, the Council of Ministers is not a supranational body but an intergovernmental one.
It should not be confused with the European Council, which is the name given to the regular meetings - sometimes called summits - of the EU member states' heads of state or government.