4 AuCl3 + 3 H2O2 + 6 KOH → 6 KCl2 + 4 Au + 3 O2 + 6 H2O
This is an oxidation-reduction (redox) reaction:
4 AuIII + 12 e- → 4 Au0 (reduction)
6 KI - 6 e- → 6 KII (oxidation)
6 O-I - 6 e- → 6 O0 (oxidation)
AuCl3 is an oxidizing agent, KOH is a reducing agent, H2O2 is a reducing agent.