The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with more than 1.25 billion members worldwide. One of the oldest religious institutions in the world, it has played a prominent role in the history of Western civilisation.  Headed by the Bishop of Rome, known as the Pope, its doctrines are summarised in the Nicene Creed. The Catholic Church is also notable within the Western Christian tradition for its celebration of the seven sacraments.