Current that flows steadily in one direction is called direct current - like in batteries. It contains free charged particles mostly electrons sometimes ions that can move through this material. 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.