Incenses are a special class of held items that help Pokémon to breed differently. This allows Pokémon to produce Eggs containing baby Pokémon that were introduced beyond Generation II if the baby Pokémon was introduced after its evolutionary relatives.
Notably, most baby Pokémon which result from Incense breeding have different Egg move lists than their evolved forms. For example, Azurill can learn Fake Tears through breeding while Marill cannot, and Marill can learn Aqua Jet through breeding while Azurill cannot.
List of incenses