The Privy Council goes back to the earliest days of the Monarchy, when it comprised those appointed by the King or Queen to advise on matters of state. As the constitution developed into today's constitutional monarchy, under which The Sovereign acts on the advice of Ministers, so the Privy Council adapted. Its day to day business is transacted by those of Her Majesty's Ministers who are Privy Counsellors, that is all Cabinet Ministers and a number of junior Ministers. Membership of the Privy Council brings with it the right to be called "Right Honourable". A list of Members of the Privy Council.
The Privy Council still meets regularly, on average once a month, but, as with the Cabinet, most of its business is transacted in discussion and correspondence between its Ministerial members and the Government Departments that advise them. The Privy Council Office provides a secretariat for these discussions, as the Cabinet Office does in relation to the business of Cabinet and Cabinet Committees. Councils are held by The Queen and are attended by Ministers and the Clerk of the Council. At each meeting the Council will seek Her Majesty's formal approval to a number of Orders which have already been discussed and approved by Ministers, much as Acts of Parliament become law through the giving of the Royal Assent after having been debated in Parliament.
Meetings are reported in the Court Circular, along with the names of Ministers attending (usually four in number). The Orders made at each Council are in the public domain, and each bears the date and place of the Council at which it was made. There is therefore nothing at all "secret" about Privy Council meetings. The myth that the Privy Council is a secretive body springs from the wording of the Privy Council Oath, which, in its current form, dates back to Tudor times. It requires those taking it to "keep secret all matters...treated of in Council". The Oath (or solemn affirmation for those who cannot take an Oath) is still administered, and is still binding; but it is only in very special circumstances nowadays that matters will come to a Privy Counsellor on "Privy Council terms". These will mostly concern matters of the national interest where it is important for senior members of Opposition parties to have access to Government information.