What is ionic bonding?

Ionic bonding occurs between positive and negatively charged ions. A simple example is Sodium Chloride. Sodium has 1 outer shell electron which it wants to lose in order to create a stable electronic configuration (full outer shell). Chlorine has 7 outer shell electrons so it wants to gain one more in order to form a stable electronic configuration.
So if sodium loses one electron and gives it to chlorine this solves the problem. Sodium loses one negatively charged electron and becomes positively charged (1+) whilst chlorine gains one negatively charged electron and becomes negatively charged (1-)
The oppositely charged ions attract and an ionic bond is formed.