A pheromone is a chemical produced by an animal, usually an insect, that influences the behavior or development of others of the same species, often functioning as an attractant of the opposite sex. "Love drug".
Here is a good description of what pheromones are and what effect they have on humans: http://www.fragrancex.com/customerservice/pheromones.html.
This chemical is also a trail left by the insects to indicate the other individuals of the source of food and with the help of these chemical products,other insects are able to reach the food source conveniently.We would have often witnessed the insects communicating head on with each other,and that is the way of exchanging chemical products.
Pheromones are chemicals that organisms secrete as a way of
communicating with members of their own species. For instance, ants
secrete pheremones that tell other ants where a food trail is,
while deer secrete 'alarm' chemicals the tell other deer when
threats are nearby. Many animals, humans included, secrete
pheremones that attract members of the opposite sex.
Farmones are Nature's "Love Potion".