These days taking a more ceremonial role than once was the case, the self-styled "Her Majesty's Most Honourable Privy Council" is a body of important figures whose primary purpose is as advisors to the British Sovereign.
Made up of a number of influential committees, such as the Judicial Committee and the incumbent government's Cabinet, The Privy Council is nominally appointed by the Sovereign but in reality all new Privy Councillors must be approved by the ruling party of the day.
Permanent members on the Council include the heir to the throne, senior judiciary especially appeal court judges, and the three most important clergy of the Church of England - the Archbishops of York and Canterbury and the Bishop of London.
The vast majority of Privy Councillors are politicians, in fact certain politicians - the Prime Minister and Cabinet, the Leader of the Opposition, for instance - are sworn in as a matter of course upon taking up their posts. There are also several foreign dignitaries with places on the Council, mostly senior politicians and judiciary of Commonwealth states such as Canada and New Zealand.
The Privy Council meetings themselves are attended by the Sovereign, who must approve or decline the Council's orders (although the last time anything was declined was several centuries ago), and all members are required to stand so, understandably, business is conducted with brevity.