The Admiralty was formerly the authority in the Kingdom of England, and later in the United Kingdom, responsible for the command of the Royal Navy. Originally exercised by a single person, the office of Lord High Admiral was from the 18th century onward almost invariably put "in commission" and exercised by the Lords Commissioners of the Admiralty, who sat on the Board of Admiralty.
In 1964, the functions of the Admiralty were transferred to a new Admiralty Board, which is a committee of the tri-service Defence Council of the United Kingdom and part of the Ministry of Defence. The new Admiralty Board meets only twice a year, and the day-to-day running of the Royal Navy is controlled by a Navy Board (not to be confused with the historical Navy Board described later in this article). It is common for the various authorities now in charge of the Royal Navy to be referred to as simply The Admiralty.
The title of Lord High Admiral of the United Kingdom was vested in the Sovereign from 1964 to 2011. The title was awarded to The Duke of Edinburgh by the Queen on his 90th birthday. There also continues to be a Vice-Admiral of the United Kingdom and a Rear-Admiral of the United Kingdom, both of which are honorary offices.
Read more about Admiralty: Admiralty Buildings, "Admiralty" As A Metonym For "sea Power"