2 KBrO3 + 6 KI + 6 H2SO4 → 3 I2 + 2 BrSO4 + 4 K2SO4 + 6 H2O
This is an oxidation-reduction (redox) reaction:
2 BrV + 12 e- → 2 Br-I (reduction)
2 SVI - 6 e- → 2 SIX (oxidation)
6 I-I - 6 e- → 6 I0 (oxidation)
KBrO3 is an oxidizing agent, H2SO4 is a reducing agent, KI is a reducing agent.