Conductor and insulators

All material can be divided into three eletrical catogories. A material is either a conductot ; or it is an insulator or it lies somewhere between the two and is called semi-conductor.
A conductor is a material which has very little resistance toncurrent low. In other words, it allows current to flow easily. Metals widely used as a conductor include copper and silver wires. Carbon and ordinary water are also good-conductors.
An insulator is a material which offers very strong resistance (opposition) to the flow of current.In other words,it does not allow current to flow easily.Glass,paper,rubber,ceramics and certain plastic materials are much used as insulators in electrical equipment.
In the last few years, those material which fall between conductors and insulators are known as semiconductors,have become very important;for example, these materials are used mostly in rectifiers and transistors.