Igloos, which are entirely built of snow blocks, have mostly been constructed by the Inuit tribes that live in parts of Canada and Greenland. Other Inuit groups have used snow, instead, to insulate homes made from other materials. Some igloos are built for temporary shelter, while others are permanent, warm housing in very cold climates. The noun igloo comes from an Inuit word, iglu, which means simply "house," no matter what it's constructed from.