What is the difference between conductors and insulators?

Conductors are materials that allow electric current to flow easily because they have free electrons — examples include copper, aluminum, silver, and gold. Insulators resist or block current flow because their electrons are tightly bound — examples include rubber, glass, plastic, and dry wood. This is why wires use copper (conductor) wrapped in plastic or rubber (insulator). Knowing which materials conduct and which insulate is fundamental electronics content. Semiconductors, like silicon, fall between the two and conduct under certain conditions, forming the basis of modern electronic components.