When the reactant and products involved in a chemical change are ionic compounds, these will be present in the form of ions in the solution. The chemical change is written in ionic forms in the chemical equation, it is termed as ionic equation.
Example: MnO2 + 4H+ + 4Cl- → Mn2++ 2Cl- + 2H2O +Cl2
In the above example, the reactant and products have been written in ionic forms, thus the equation is termed as ionic equation.