The Evolving European Union
The European Union (EU) has evolved greatly since its inception (in 1951) as the European Coal and Steel Community, an inspiration of French foreign minister Robert Schumann with the explicit aim of using economic self-interest to drive the political union of war-ravaged France and Germany. Five countries immediately expressed interest in joining France: Germany, Italy and the 3 Benelux countries. The founding treaty of Paris created a supra-national ‘High Authority’ which eventually became the Commission, but almost immediately tension began to develop, as the component national governments (particularly France) resented their loss of sovereignty, and used the inter-national ‘Council of Ministers’ to control the power of the supra-national ‘Commission’. The present-day (2016) European Union is defined in the 2007 Treaty on European Union. But the institution continues to develop informally under the stresses of the times, such as the lingering debt crisis that has followed the collapse of numerous banks in 2008, and the immigration that has resulted from instability in the middle-east.
The Treaty on European Union (2007) establishes and names the 7 institutions in the following order.
 The European Parliament (EP) is the directly elected parliamentary institution of the European Union (EU). Together with the Council of the European Union (the Council) and the European Commission, it exercises the legislative function of the EU. The Parliament is composed of 751 members, who represent the largest trans-national democratic electorate in the world (375 million eligible voters in 2009). It has been directly elected every five years by universal suffrage since 1979.
The European Parliament is the supreme institution in the EU; it therefore supervises the executive body of the EU (the European Commission) which is thus accountable to Parliament. In particular, Parliament (since 2014) elects the President of the Commission, and approves (or rejects) the appointment of the Commission as a whole. It can force the Commission to resign as a body by adopting a motion of censure.
 The European Council is the institution of the European Union (EU) that comprises the heads of state or government of the member states, along with President of the European Council and the President of the European Commission. The High Representative of the Union for Foreign Affairs and Security Policy also takes part in its meetings. Established as an informal summit in 1975, the European Council was formalised as an institution in 2007 by the Treaty of Lisbon, which came into force in 2009.
 The Council of the European Union (often still called the 'Council of Ministers' as contrasted with 'Council of Heads', or sometimes just called the Council). It is part of the essentially bicameral EU legislature (the other legislative body being the European Parliament), but resembles more the USA Senate than the British House of Lords. It represents the executive governments of the EU's member states. It is based in Brussels. Its origen dates from the early fifties, when its role was to curb the Commission (inter-national curbing Supra-national).
 The European Commission (EC) is the oldest of the institutions, founded in 1951 as the supra-national authority of the Coal and Steel Community. The Commission is the executive body of the EU responsible for proposing legislation, implementing decisions, upholding the EU treaties and managing the day-to-day business of the EU. Commissioners swear an oath at the European Court of Justice in Luxembourg, pledging to respect the treaties and to be completely independent in carrying out their duties during their mandate.
The Commission operates as a 'cabinet government', with 28 members of the Commission (informally known as "commissioners"). There is one member per member state, though commissioners are bound by oath to represent the interests of the EU as a whole rather than their home state. One of the 28 is the Commission President (currently Jean-Claude Juncker) proposed by the European Council but elected by the European Parliament. The Council then appoints the other 27 members of the Commission in agreement with the nominated President, and the 28 members as a single body are then subject to a vote of approval by the European Parliament. The current Commission (the 'Juncker Commission') took office in late 2014 and will run till 2019 (unless censured). The President of the Commission together with the President of the European Council and the High Representative of the Union for Foreign Affairs and Security Policy, represents the EU abroad.
The term ‘Commission’ is used either in the narrow sense of the 28-member College of Commissioners (or College) but also to include the administrative body of about 23,000 European civil servants who are split into departments called directorates-general and services. The procedural languages of the Commission are English, French and German. The Members of the Commission (and their immediate secretariats) are based in Brussels.
 The Court of Justice of the European Union (CJEU) is the institution of the European Union that encompasses the whole judiciary. Sited in Luxembourg, it now consists of three separate courts: the ‘Court of Justice’ (see below), the General Court and the Civil Service Tribunal. It originated in 1952 to clarify the law of the new institutions. It is not to be confused with the ‘European Court of Human Rights’ (the supranational court based in Strasbourg); nor with the 'European Court of Justice' (the CJEU's Court of Justice), the highest court of the CJEU.)
 The European Central Bank (ECB) is the central bank for the euro and administers monetary policy of the Eurozone, which consists of 19 EU member states and is one of the largest currency areas in the world. It is one of the world's most important central banks, and is mandated to maintain price stability (and to define and implement the monetary policy for the Eurozone, and to conduct foreign exchange operations). The capital stock of the bank is owned by the central banks of all 28 EU member states. The Treaty of Amsterdam established the bank in 1998, and it is based in Frankfurt.
 The Court of Auditors was established in 1975 in Luxembourg to audit the accounts of EU institutions. The Court is composed of one member from each EU member state, one of whom is chosen to be its president.
(The above is deeply indebted to Wikipedia. I propose to continue in a separate post to discuss the tensions, and weaknesses, in the current institutions.)