An insulator is a material that does not allow electric charges (usually electrons) to move freely through it. It has high resistivity and does not conduct electricity easily.
Related terms
Conductor: A conductor is the opposite of an insulator. It is a material that allows electric charges to move freely through it.
Band Gap: The band gap is the energy range in which no electron states are available for conduction in an insulator or semiconductor.
In the context of insulators, polarization refers to the separation of positive and negative charges within a material when subjected to an external electric field.