The Channel Islands lie in the English Channel off the coast of Normandy - Jersey, Guernsey, Alderney, Sark and Herm, and smaller isles.
There are two British Crown Dependencies, the Bailiwick of Jersey and the Bailiwick of Guernsey (which also includes Alderney, Sark and Herm). They're neither part of the United Kingdom or European Union, but are "possessions" of the Crown (like the Isle of Man) and their residents are British citizens.