An insulator is a substance that does not conduct energy well. Insulators are commonly used to contain electricity, and make it safe to use commonly. Glass, porcelain, and plastic is commonly used for this purpose.
A thermal insulator is a substance that conducts heat poorly, such as hotpads for kitchen use, or home insulation to avoid heat loss during winter. Air is a very good thermal insulator, so most insulation for heat contains pockets, bubbles, and regions of air. A vacuum insulates heat even better, since there are no atomic particles available to transfer the heat away.
- Wile, Dr. Jay L. Exploring Creation With Physical Science. Apologia Educational Ministries, Inc. 1999, 2000