The term flag state emerged from the early use of flags as a symbol of the nationality or tribe to whom the ships belonged. The flag has evolved into an officially sanctioned and extremely potent symbol of the state, serving as tangible evidence of the nationality given by the state to ships registered under its laws. The ship's flag displays the ship's nationality and the laws that govern its operation in international seas.
It should be noted, however, that not all vessels are registered in the nation of origin of their ship owners. The country under which such vessels operate is known as the flag state, whilst the practice of registering the ship in a state other than the ship's owner is known as the flag of convenience (FOC).