Answer is: conductivity in solution and solubility in water.
Ionic compounds conduct electricity, because it dissociate in ions and ions conduct electicity.
Ionic substances dissociate in water on cations and anions. For example, dissociation of potassium chloride in water: KCl(aq) → K⁺(aq) + Cl⁻(aq).
Ionic compounds (most of the salts, strong acids and bases) dissolve in water because an ion-dipole interactions.
An ion-dipole is electrostatic interaction between a charged ion (cations and anions) and a molecule that has a dipole (in this example water).
Dipole is a separation of positive and negative charges. In water, hydrogen has positive and oxygen has negative charge.
