It is an electrostatic attraction between two oppositely charged atoms.
All atoms try to be more "chemically stable" by gaining or losing electrons to reach the same number of electrons as the nearest noble gas in the periodic table. However, this gain or loss of electrons will render them either positive (electron loss) or negative (electron gain).
The resulting atoms will be chemically stable but not neutrally charged. This will cause them to be attracted to each other and stick together.
A good example is table salt, Sodium Chloride.
When they both get in contact with each other, the single atom of
This change in electrical charge will turn
Ionic bonds are one of the strongest type of bonds and are water soluble due to their strong polarity.