MnIVO2 + 2 NaCl-I + 2 H2SO4 Na2SO4 + MnIISO4 + Cl20 + 2 H2O

This is an oxidation-reduction (redox) reaction:

MnIV + 2 e- MnII (reduction)

2 Cl-I - 2 e- 2 Cl0 (oxidation)

MnO2 is an oxidizing agent, NaCl is a reducing agent.