3 Fe0 + 2 KNVO3 + 8 HCl 3 FeIICl2 + 2 KCl + 2 NIIO + 4 H2O

This is an oxidation-reduction (redox) reaction:

2 NV + 6 e- 2 NII (reduction)

3 Fe0 - 6 e- 3 FeII (oxidation)

KNO3 is an oxidizing agent, Fe is a reducing agent.