An insulator is a material that resists the flow of electric current or heat. Common examples include rubber, glass, and certain plastics. Insulators are essential in electrical systems, as they prevent unwanted current from escaping and protect users from electric shocks. In addition to electricity, insulators also play a crucial role in thermal applications. For instance, materials like foam and fiberglass are used in building insulation to keep homes warm in winter and cool in summer. By reducing heat transfer, insulators help improve energy efficiency and comfort in various environments.