From the longer Wikipedia page 
The Crown dependencies (French: Dépendances de la Couronne; Manx: Croghaneyn-crooin) are three island territories off the coast of Great Britain that are self-governing possessions of The Crown: the Bailiwick of Guernsey, the Bailiwick of Jersey and the Isle of Man. They do not form part of either the United Kingdom or the British Overseas Territories. Internationally, the dependencies are considered "territories for which the United Kingdom is responsible", rather than sovereign states. As a result, they are not member states of the Commonwealth of Nations. However, they do have relationships with the Commonwealth, the European Union, and other international organisations, and are members of the British–Irish Council. They have their own teams in the Commonwealth Games. They are not part of the European Union (EU), although they are within the EU's customs area. The Isle of Man (along with the United Kingdom) is within the EU VAT area.
As the Crown dependencies are not sovereign states, the power to pass legislation affecting the islands ultimately rests with the government of the United Kingdom (though this is rarely done without the consent of the dependencies, and the right to do so is disputed). However, they each have their own legislative assembly, with the power to legislate on many local matters with the assent of the Crown (Privy Council, or in the case of the Isle of Man in certain circumstances the Lieutenant-Governor). In each case, the head of government is called the Chief Minister.