2.19 Identify common materials which are electrical conductors or insulators, including metals and plastics

Insulators do not carry an electrical current through them. They are usually non-metals, with some exceptions. These materials have a very high resistance. 
Eg: Plastic


Electrical conductors, as the name suggests, do carry an electrical current. These are metals. Copper, for example, is a very good electrical conductor because it has a very low resistance.