An ambassador is the official representative of one state to another or to an international organization such as the United Nations. Representatives of the mission in cities other than the capital are called consuls. The host country typically allows the ambassador and any consuls control of specific territory called an embassy or consulate respectively. The territory, staff and even vehicles used by the mission are usually afforded diplomatic immunity to most laws of the host country.
Ambassadors to the United Kingdom are officially titled Ambassador to the Court of St. James.