What is Ionic compound?

An ionic compound is made of cations and anions in such numbers that the whole carries no charge. Its formula gives the proportion of the ions, without their charges: $\ce{NaCl}$ for sodium chloride, one $\ce{Na+}$ for each $\ce{Cl-}$; $\ce{CaCl2}$ for calcium chloride, two $\ce{Cl-}$ for each $\ce{Ca^{2+}}$.