Electrons in all conductive materials (conductors), provide the movement of electric current. Electrons move in a conductor from atom to atom. Non-conductive materials (insulators), also have electrons that are associated with the atomic nucleus. They cannot move and are not conductors of electric current.
The third group of materials is the so-called semiconductors. Are these crystals (in most cases germanium or silicon), the structure of atoms, which allows them to have extra electrons or an insufficient number of them. Due to this, an effect is created in which an electric current can pass through their crystal lattices only under certain conditions. If these conditions are not met, an insulating layer is built. Semiconductor elements are in most cases interlocked into entire switch systems, such as in the ignition and injection control unit.