5 Cl2 (g) + 12 NaOH (aq) + Br2 (aq) → 6 H2O (l) + 10 NaCl (aq) + 2 NaBrO3 (aq)
This is an oxidation-reduction (redox) reaction:
2 Br0 - 10 e- → 2 BrV (oxidation)
10 Cl0 + 10 e- → 10 Cl-I (reduction)
Br2 is a reducing agent, Cl2 is an oxidizing agent.