What is an oxidation reaction? Identify in the following reaction

What is an oxidation reaction? Identify in the following reaction
(i) the substance oxidized.
(ii) the substance reduced

ZnO → Zn + CO

Oxidation reaction is one which involves gain of oxygen or loss of hydrogen. In the reaction
ZnO + C → Zn + CO

(i) C is oxidised to CO.
(ii) ZnO is to reduced Zn.