A British Crown Dependency is a self-governing territory that is not part of the United Kingdom but is under the sovereignty of the British monarch. The three main Crown Dependencies are Jersey, Guernsey, and Isle of Man. Each has its own legal system and government, allowing them to manage their own affairs, including taxation and legislation. While they are not represented in the UK Parliament, the Crown Dependencies maintain a close relationship with the UK for defense and international representation. They are responsible for their own internal matters, but the UK is responsible for their defense and international relations.