KIO4 (s) + 7 KI (aq) + 4 H2SO4 (aq) → 4 I2 (s) + 4 K2SO4 (aq) + 4 H2O (l)
This is an oxidation-reduction (redox) reaction:
7 I-I - 7 e- → 7 I0 (oxidation)
IVII + 7 e- → I0 (reduction)
KI is a reducing agent, KIO4 is an oxidizing agent (synproportionation (comproportionation)).