KBrO3 (aq) + 3 H2SO4 (aq) + 5 KBr (aq) → 3 Br2 (aq) + 3 K2SO4 (aq) + 3 H2O (l)
This is an oxidation-reduction (redox) reaction:
5 Br-I - 5 e- → 5 Br0 (oxidation)
BrV + 5 e- → Br0 (reduction)
KBr is a reducing agent, KBrO3 is an oxidizing agent (synproportionation (comproportionation)).