Answer:
A combustion reaction is a major class of chemical reactions, commonly referred to as "burning." Combustion usually occurs when a hydrocarbon reacts with oxygen to produce carbon dioxide and water.
Step-by-step explanation:
Burning wood in air is an exothermic process (it releases heat), but there is an energy barrier, so it requires a bit of heat in the beginning to get the reactions started. Wood reacts with oxygen in the air to form (mostly) carbon dioxide and water vapor.