What is the difference between complete and incomplete combustion of a hydrocarbon?

In complete combustion, there is a sufficient supply of oxygen which is able to react with the burning hydrocarbon allowing the reaction products H₂O and CO₂ to be formed.
In incomplete combustion there is a lack of oxygen so when heat is applied carbon monoxide is released.
For example: C₂H₆ + 3 ¹/₂O₂ -> 2CO₂ + 3H₂O C₂H₆ + 3O₂ -> CO + CO₂ + 3H₂O