What makes a conductor different from an insulator?

Why are conductors different from insulators ?

Is human body a conductor or an insulator?

Conductors and insulators

Is our body a conductor or an insulator.

What is thermal conductivity of a perfect heat conductor and perfect heat insulator?

What is thermal conductivity of a perfect heat conductors of a perfect heat conductor and a perfect heat insulator?

According to energy band diagram, what makes a substance conductor insulator?