Generally metals are good conductors. An insulator has the opposite properties of a conductor. It does not allow electric charges to flow through it. Insulators are important for electrical safety. Glass, rubber, plastic, dry wood, dry air are good insulators.
Resistance is material's opposition to the conduction of electric flow.
Resistance occurs when electrons moving in the material hit the atoms and give up energy in form of heat. A good conductor has low resistance. The semiconductor has higher resistance and insulators have so high resistance, that electric flow through them is not possible. Everybody from as has already experienced the static electricity in the form of a slight electric shock. An example is when you walk across a rug on a dry day.