In conductors electrons are fairly free to move and so we can have flow of electrical charge. Again this gives us a further clue. Electrical current is the rate of flow of electric charge. We need to study a little chemistry here. We are all familiar with sodium chloride or common salt.
Sodium chloride is formed by the combination of sodium and chlorine.
So we have sodium ions which are positively charged and chloride ions which are negatively charged. In this solid the attraction between the sodium ions and the chloride ions is strong and it is difficult to separate them. Sodium chloride is an ionic compound, that is the components are present as ions. If we try to pass an electric current through sodium chloride we find that there is considerable resistance to the flow - salt doesn't conduct. The solid dissolves, and the ions separate.