The elements combine with other elements in order to complete their octet and attain stability. The combination can take place either by transfer of electrons or by sharing of electrons. The sharing of electrons results in formation of covalent bond whereas transfer of electrons results in the formation of ionic bonds. The loss of electrons will result in the formation of cation whereas the gain of electrons results in formation of anion. The two oppositely charged ions are held together by electrostatic force of attraction between them.
Hence, an ionic is a force that holds two oppositely charged ions together.