Short answers, pulled from the story.
The Channel Islands are not part of the United Kingdom. They are Crown Dependencies, meaning the UK is responsible for their defence and international relations, but they govern themselves independently with their own laws, legislatures, and courts. They have been administered as two separate bailiwicks since the late 13th century.
The Channel Islands were occupied by the German Army from 1940 to 1945. The British Government demilitarised the islands in June 1940 before German troops landed between the 30th of June and the 4th of July 1940. Over 2,000 islanders were deported, Jews were sent to concentration camps, and in Alderney alone, four prison camps housed approximately 6,000 people, of whom over 700 died. Jersey and Guernsey were liberated on the 9th of May 1945.
Victor Hugo lived in exile in the Channel Islands, first in Jersey and then in Guernsey, where he completed Les Misérables. He also set his later novel Les Travailleurs de la Mer (Toilers of the Sea) in Guernsey. Herman Melville included a "Guernsey-man" character in chapter 91 of Moby-Dick.
English is the predominant language today, following Anglicisation in the 19th century. Four dialects of Norman were historically spoken: Jèrriais in Jersey, Dgèrnésiais in Guernsey, Sercquiais in Sark, and Auregnais in Alderney, which became extinct in the late 20th century. Jèrriais and Guernésiais are recognised as regional languages of the islands.
Jersey and Guernsey developed into major offshore financial centres from the 1960s, aided by income from offshore finance and the decision not to join the European Economic Community when the UK joined. By 2018, financial services accounted for 39.4% of Jersey's Gross Value Added. Despite having around 250,000 residents, the Channel Islands combined with the Isle of Man are the second-biggest source of foreign direct investment in the United Kingdom.
The term "Channel Islands" began to be used around 1830, possibly first by the Royal Navy as a collective name for the archipelago off the French coast of Normandy. The term refers specifically to the islands west of the Cotentin Peninsula. Other islands in the English Channel, such as the Isle of Wight, are not considered Channel Islands.