The Privy Council, as body of government, predates the Cabinet and the existence of the Prime Minister by many centuries. Originally the private council of trusted advisers surrounding the sovereign, it has evolved to become a somewhat hidden instrument of government. It also has judicial powers (as the appeal court for some Commonwealth nations and for devolution cases) and roles relating to chartered organisations and universities.
For the purposes of government, the functional Council is made up of the Cabinet and some Ministers of State as well as the Leader of the Opposition, which permits the sharing of information, such as intelligence material, at the highest level on 'Privy Council terms'.
Privy Counsellors take an oath of confidentiality and, styled as Rt Hon, remain members for life, although their levels of activity may increase or decrease over time. Many former Ministers are inactive members of the Council. By convention the Leader of either the House of Commons or the House of Lords holds the title 'Lord President of the Council'.
As far as government goes, the Privy Council legislates by making of Orders in Council (some of which have been approved by Parliament) in line with the operation of the Royal Prerogative and powers accorded to it by statute. The monarch assents to the Orders and statutory instruments that have been agreed by Ministers.
Meetings of the Council take place about nine times a year in the presence of the monarch, normally at Buckingham Palace, although Ministers may have to travel if the monarch is at another royal residence. An attendance of four Ministers and the Clerk of the Council (a civil servant) is usual. Meetings are brief and conducted standing up.