The word equation for the burning of a candle is wax plus oxygen yields carbon dioxide and water. This is an exothermic reaction that produces both light and heat.
The fuel for a burning candle is the wax. There are many different types of wax with a corresponding number of chemical formulas, but they are all hydrocarbons. Hydrocarbons are molecules made from hydrogen and carbon.
Burning the wax pulls the hydrogen and carbon in the wax apart and recombines them with oxygen from the atmosphere. This is an oxidation reaction. The resulting carbon dioxide and water are gases that disperse in the air.