NaO + Al + 3 H2O → Na[Al(OH)4] + H2
This is a complexation reaction: Na[Al(OH)4] is the formed complex.
This is an oxidation-reduction (redox) reaction:
2 HI + 2 e- → 2 H0 (reduction)
Al0 - 3 e- → AlIII (oxidation)
O-I + e- → O-II (reduction)
H2O is an oxidizing agent, Al is a reducing agent, NaO is an oxidizing agent.