Ionic bonds result when electrons are transfered between atoms forming ions.
The electron donor will become a positively charged ion = cation
The electron acceptor will become a negatively charged ion = anion
The ionic bonds then result from the non-directional, electrostatic interaction between the ions based on simple electrostatics.
Mathematically, ionic bonds are formed when the electronegativity difference (Δχ) between the atoms is > 1.7 Debye