The fundamental difference lies in their ability to conduct electricity. A conductor allows electrons to flow freely, facilitating the transfer of electrical energy. In contrast, an insulator is a material that strongly resists the flow of electric current. This is due to its atomic structure, where electrons are tightly bound and cannot move freely. Insulators like rubber, plastic, and porcelain are essential for safety, as they are used to coat wires, prevent electrical shocks, and separate conductive components.