Simply sheets of pliable aluminum that are less than 0.2 mm thick, aluminum foil has several household uses. Some companies manufacture long, stronger strips specifically for insulation, but you can also use typical aluminum foil to insulate. If the foil is particularly thin, companies will sometimes laminate it with plastic, paper or other materials to make it stronger.
Because aluminum foil reflects light, it can be used for insulation, especially in areas that need to be guarded against heat. When it is used with other materials, it can be used to warm an area, too. Other materials such as paper and cotton, do not have the reflectivity that aluminum foil does, so when the sun is bearing down, they will not keep it out as well. An area that is already hot will be kept hot by aluminum foil, as it will hold in hot air. Paper and cotton will release heat at a quicker rate than aluminum foil. Aluminum foil can keep things like wires or pipes insulated, as it traps air when it is wrapped around an object. This can be achieved with several objects, though, and not just aluminum foil.