Shipping is an international industry, and the flag of a vessel shows where in the world it is registered, which is known as a flag state. The flag and port name can be seen on the stern of the ship.
The Commonwealth of Dominica Maritime Administration
You could say that a ship is a tiny piece of the country where that ship is registered. The rules and regulations of that country apply on the ship, no matter where in the world the ship is.
However, a ship is not a piece of land. It performs a...
https://maritime-professionals.com/what-does-a-responsible-flag-state-do/