What are conductors and non-conductors?
In terms of electricity there are two main classes of material: namely: conductors and non-conductors (or insulators). From their names it can be gathered that conductors will conduct electricity freely, whereas non-conductors act as insulators preventing the flow of an electric current.
An electric current is made up of the flow of electrons. This means that for a current to flow, the electrons must be able to move freely within the material. In some materials electrons are moving freely around the lattice, not particularly attached to a given electron. At any instance electrons are moving freely but randomly. By placing a potential difference across the conductor the electrons can be made to drift in one direction and this constitutes an electric current. Metals are all conductors of electricity, and a number of other substances also conduct it to varying degrees.
Other substances do not have electrons moving freely around the lattice. Electrons are firmly held within their molecules and cannot escape easily. Accordingly when a potential is placed across the substance very few electrons will move and very little or no current will flow. These substances are called non-conductors or insulators. They include most plastics, ceramics and many naturally occurring substances like wood.